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145.635s142.011-65.374 142.011-145.635c0-8.803 6.99-15.793 15.794-15.793s15.793 6.99 15.793 15.793c0 95.019-73.789 172.82-165.96 177.093z"></path></svg><span>About 59 min</span><meta property="timeRequired" content="PT59M"></span><!----><!----></div><hr></div><div class="vp-toc-placeholder"><aside id="toc"><!--[--><!----><!--]--><div class="vp-toc-header">On This Page<button type="button" class="print-button" title="Print"><svg xmlns="http://www.w3.org/2000/svg" class="icon print-icon" viewBox="0 0 1024 1024" fill="currentColor" aria-label="print icon"><path d="M819.2 364.8h-44.8V128c0-17.067-14.933-32-32-32H281.6c-17.067 0-32 14.933-32 32v236.8h-44.8C145.067 364.8 96 413.867 96 473.6v192c0 59.733 49.067 108.8 108.8 108.8h44.8V896c0 17.067 14.933 32 32 32h460.8c17.067 0 32-14.933 32-32V774.4h44.8c59.733 0 108.8-49.067 108.8-108.8v-192c0-59.733-49.067-108.8-108.8-108.8zM313.6 160h396.8v204.8H313.6V160zm396.8 704H313.6V620.8h396.8V864zM864 665.6c0 25.6-19.2 44.8-44.8 44.8h-44.8V588.8c0-17.067-14.933-32-32-32H281.6c-17.067 0-32 14.933-32 32v121.6h-44.8c-25.6 0-44.8-19.2-44.8-44.8v-192c0-25.6 19.2-44.8 44.8-44.8h614.4c25.6 0 44.8 19.2 44.8 44.8v192z"></path></svg></button><div class="arrow end"></div></div><div class="vp-toc-wrapper"><ul class="vp-toc-list"><!--[--><li class="vp-toc-item"><a class="route-link vp-toc-link level2" href="#overview">OVERVIEW</a></li><li><ul class="vp-toc-list"><!--[--><li class="vp-toc-item"><a class="route-link vp-toc-link level3" href="#syntax-definition">Syntax Definition</a></li><!----><!--]--><!--[--><li class="vp-toc-item"><a class="route-link vp-toc-link level3" href="#syntax-description">Syntax Description</a></li><!----><!--]--><!--[--><li class="vp-toc-item"><a class="route-link vp-toc-link level3" href="#basic-examples">Basic Examples</a></li><!----><!--]--><!--[--><li class="vp-toc-item"><a class="route-link vp-toc-link level3" href="#execution-interface">Execution Interface</a></li><!----><!--]--></ul></li><!--]--><!--[--><li class="vp-toc-item"><a class="route-link vp-toc-link level2" href="#select-clause-1">SELECT CLAUSE</a></li><li><ul class="vp-toc-list"><!--[--><li class="vp-toc-item"><a class="route-link vp-toc-link level3" href="#last-query">Last Query</a></li><!----><!--]--></ul></li><!--]--><!--[--><li class="vp-toc-item"><a class="route-link vp-toc-link level2" href="#where-clause-1">WHERE CLAUSE</a></li><li><ul class="vp-toc-list"><!--[--><li class="vp-toc-item"><a class="route-link vp-toc-link level3" href="#time-filter">Time Filter</a></li><!----><!--]--><!--[--><li class="vp-toc-item"><a class="route-link vp-toc-link level3" href="#value-filter">Value Filter</a></li><!----><!--]--><!--[--><li class="vp-toc-item"><a class="route-link vp-toc-link level3" href="#fuzzy-query">Fuzzy Query</a></li><!----><!--]--></ul></li><!--]--><!--[--><li class="vp-toc-item"><a class="route-link vp-toc-link level2" href="#group-by-clause-1">GROUP BY CLAUSE</a></li><li><ul class="vp-toc-list"><!--[--><li class="vp-toc-item"><a class="route-link vp-toc-link level3" href="#aggregate-by-segment">Aggregate By Segment</a></li><!----><!--]--><!--[--><li class="vp-toc-item"><a class="route-link vp-toc-link level3" href="#aggregate-by-group">Aggregate By Group</a></li><!----><!--]--></ul></li><!--]--><!--[--><li class="vp-toc-item"><a class="route-link vp-toc-link level2" href="#having-clause-1">HAVING CLAUSE</a></li><!----><!--]--><!--[--><li class="vp-toc-item"><a class="route-link vp-toc-link level2" href="#fill-clause-1">FILL CLAUSE</a></li><li><ul class="vp-toc-list"><!--[--><li class="vp-toc-item"><a class="route-link vp-toc-link level3" href="#introduction">Introduction</a></li><!----><!--]--><!--[--><li class="vp-toc-item"><a class="route-link vp-toc-link level3" href="#syntax-definition-1">Syntax Definition</a></li><!----><!--]--><!--[--><li class="vp-toc-item"><a class="route-link vp-toc-link level3" href="#fill-methods">Fill Methods</a></li><!----><!--]--></ul></li><!--]--><!--[--><li class="vp-toc-item"><a class="route-link vp-toc-link level2" href="#limit-and-slimit-clauses-pagination">LIMIT and SLIMIT CLAUSES (PAGINATION)</a></li><li><ul class="vp-toc-list"><!--[--><li class="vp-toc-item"><a class="route-link vp-toc-link level3" href="#row-control-over-query-results">Row Control over Query Results</a></li><!----><!--]--><!--[--><li class="vp-toc-item"><a class="route-link vp-toc-link level3" href="#column-control-over-query-results">Column Control over Query Results</a></li><!----><!--]--><!--[--><li class="vp-toc-item"><a class="route-link vp-toc-link level3" href="#row-and-column-control-over-query-results">Row and Column Control over Query Results</a></li><!----><!--]--><!--[--><li class="vp-toc-item"><a class="route-link vp-toc-link level3" href="#error-handling">Error Handling</a></li><!----><!--]--></ul></li><!--]--><!--[--><li class="vp-toc-item"><a class="route-link vp-toc-link level2" href="#order-by-clause-1">ORDER BY CLAUSE</a></li><li><ul class="vp-toc-list"><!--[--><li class="vp-toc-item"><a class="route-link vp-toc-link level3" href="#order-by-in-align-by-time-mode">Order by in ALIGN BY TIME mode</a></li><!----><!--]--><!--[--><li class="vp-toc-item"><a class="route-link vp-toc-link level3" href="#order-by-in-align-by-device-mode">Order by in ALIGN BY DEVICE mode</a></li><!----><!--]--><!--[--><li class="vp-toc-item"><a class="route-link vp-toc-link level3" href="#order-by-arbitrary-expressions">Order by arbitrary expressions</a></li><!----><!--]--></ul></li><!--]--><!--[--><li class="vp-toc-item"><a class="route-link vp-toc-link level2" href="#align-by-clause-1">ALIGN BY CLAUSE</a></li><li><ul class="vp-toc-list"><!--[--><li class="vp-toc-item"><a class="route-link vp-toc-link level3" href="#align-by-device">Align by Device</a></li><!----><!--]--><!--[--><li class="vp-toc-item"><a class="route-link vp-toc-link level3" href="#ordering-in-align-by-device">Ordering in ALIGN BY DEVICE</a></li><!----><!--]--></ul></li><!--]--><!--[--><li class="vp-toc-item"><a class="route-link vp-toc-link level2" href="#into-clause-query-write-back">INTO CLAUSE (QUERY WRITE-BACK)</a></li><li><ul class="vp-toc-list"><!--[--><li class="vp-toc-item"><a class="route-link vp-toc-link level3" href="#sql-syntax">SQL Syntax</a></li><!----><!--]--><!--[--><li class="vp-toc-item"><a class="route-link vp-toc-link level3" href="#application-examples">Application examples</a></li><!----><!--]--><!--[--><li class="vp-toc-item"><a class="route-link vp-toc-link level3" href="#user-permission-management">User Permission Management</a></li><!----><!--]--><!--[--><li class="vp-toc-item"><a class="route-link vp-toc-link level3" href="#configurable-properties">Configurable Properties</a></li><!----><!--]--></ul></li><!--]--></ul><div class="vp-toc-marker" style="top:-1.7rem;"></div></div><!--[--><!----><!--]--></aside></div><!--[--><!----><!--]--><div class="theme-hope-content"><h1 id="query-data" tabindex="-1"><a class="header-anchor" href="#query-data"><span>Query Data</span></a></h1><h2 id="overview" tabindex="-1"><a class="header-anchor" href="#overview"><span>OVERVIEW</span></a></h2><h3 id="syntax-definition" tabindex="-1"><a class="header-anchor" href="#syntax-definition"><span>Syntax Definition</span></a></h3><p>In IoTDB, <code>SELECT</code> statement is used to retrieve data from one or more selected time series. Here is the syntax definition of <code>SELECT</code> statement:</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">SELECT</span> <span class="token punctuation">[</span><span class="token keyword">LAST</span><span class="token punctuation">]</span> selectExpr <span class="token punctuation">[</span><span class="token punctuation">,</span> selectExpr<span class="token punctuation">]</span> <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>
    <span class="token punctuation">[</span><span class="token keyword">INTO</span> intoItem <span class="token punctuation">[</span><span class="token punctuation">,</span> intoItem<span class="token punctuation">]</span> <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">]</span>
    <span class="token keyword">FROM</span> prefixPath <span class="token punctuation">[</span><span class="token punctuation">,</span> prefixPath<span class="token punctuation">]</span> <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>
    <span class="token punctuation">[</span><span class="token keyword">WHERE</span> whereCondition<span class="token punctuation">]</span>
    <span class="token punctuation">[</span><span class="token keyword">GROUP</span> <span class="token keyword">BY</span> {
        <span class="token punctuation">(</span><span class="token punctuation">[</span>startTime<span class="token punctuation">,</span> endTime<span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token keyword">interval</span> <span class="token punctuation">[</span><span class="token punctuation">,</span> slidingStep<span class="token punctuation">]</span><span class="token punctuation">)</span> <span class="token operator">|</span>
        <span class="token keyword">LEVEL</span> <span class="token operator">=</span> levelNum <span class="token punctuation">[</span><span class="token punctuation">,</span> levelNum<span class="token punctuation">]</span> <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span> <span class="token operator">|</span>
        TAGS<span class="token punctuation">(</span>tagKey <span class="token punctuation">[</span><span class="token punctuation">,</span> tagKey<span class="token punctuation">]</span> <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span> <span class="token punctuation">)</span> <span class="token operator">|</span>
        VARIATION<span class="token punctuation">(</span>expression<span class="token punctuation">[</span><span class="token punctuation">,</span>delta<span class="token punctuation">]</span><span class="token punctuation">[</span><span class="token punctuation">,</span>ignoreNull<span class="token operator">=</span><span class="token boolean">true</span><span class="token operator">/</span><span class="token boolean">false</span><span class="token punctuation">]</span><span class="token punctuation">)</span> <span class="token operator">|</span>
        CONDITION<span class="token punctuation">(</span>expression<span class="token punctuation">,</span><span class="token punctuation">[</span>keep<span class="token operator">&gt;</span><span class="token operator">/</span><span class="token operator">&gt;=</span><span class="token operator">/</span><span class="token operator">=</span><span class="token operator">/</span><span class="token operator">&lt;</span><span class="token operator">/</span><span class="token operator">&lt;=</span><span class="token punctuation">]</span>threshold<span class="token punctuation">[</span><span class="token punctuation">,</span>ignoreNull<span class="token operator">=</span><span class="token boolean">true</span><span class="token operator">/</span><span class="token boolean">false</span><span class="token punctuation">]</span><span class="token punctuation">)</span> <span class="token operator">|</span>
        <span class="token keyword">SESSION</span><span class="token punctuation">(</span>timeInterval<span class="token punctuation">)</span> <span class="token operator">|</span>
        <span class="token function">COUNT</span><span class="token punctuation">(</span>expression<span class="token punctuation">,</span> size<span class="token punctuation">[</span><span class="token punctuation">,</span>ignoreNull<span class="token operator">=</span><span class="token boolean">true</span><span class="token operator">/</span><span class="token boolean">false</span><span class="token punctuation">]</span><span class="token punctuation">)</span>
    }<span class="token punctuation">]</span>
    <span class="token punctuation">[</span><span class="token keyword">HAVING</span> havingCondition<span class="token punctuation">]</span>
    <span class="token punctuation">[</span><span class="token keyword">ORDER</span> <span class="token keyword">BY</span> sortKey {<span class="token keyword">ASC</span> <span class="token operator">|</span> <span class="token keyword">DESC</span>}<span class="token punctuation">]</span>
    <span class="token punctuation">[</span>FILL <span class="token punctuation">(</span>{PREVIOUS <span class="token operator">|</span> LINEAR <span class="token operator">|</span> constant}<span class="token punctuation">)</span><span class="token punctuation">]</span>
    <span class="token punctuation">[</span>SLIMIT seriesLimit<span class="token punctuation">]</span> <span class="token punctuation">[</span>SOFFSET seriesOffset<span class="token punctuation">]</span>
    <span class="token punctuation">[</span><span class="token keyword">LIMIT</span> rowLimit<span class="token punctuation">]</span> <span class="token punctuation">[</span><span class="token keyword">OFFSET</span> rowOffset<span class="token punctuation">]</span>
    <span class="token punctuation">[</span>ALIGN <span class="token keyword">BY</span> {<span class="token keyword">TIME</span> <span class="token operator">|</span> DEVICE}<span class="token punctuation">]</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><h3 id="syntax-description" tabindex="-1"><a class="header-anchor" href="#syntax-description"><span>Syntax Description</span></a></h3><h4 id="select-clause" tabindex="-1"><a class="header-anchor" href="#select-clause"><span><code>SELECT</code> clause</span></a></h4><ul><li>The <code>SELECT</code> clause specifies the output of the query, consisting of several <code>selectExpr</code>.</li><li>Each <code>selectExpr</code> defines one or more columns in the query result, which is an expression consisting of time series path suffixes, constants, functions, and operators.</li><li>Supports using <code>AS</code> to specify aliases for columns in the query result set.</li><li>Use the <code>LAST</code> keyword in the <code>SELECT</code> clause to specify that the query is the last query.</li></ul><h4 id="into-clause" tabindex="-1"><a class="header-anchor" href="#into-clause"><span><code>INTO</code> clause</span></a></h4><ul><li><code>SELECT INTO</code> is used to write query results into a series of specified time series. The <code>INTO</code> clause specifies the target time series to which query results are written.</li></ul><h4 id="from-clause" tabindex="-1"><a class="header-anchor" href="#from-clause"><span><code>FROM</code> clause</span></a></h4><ul><li>The <code>FROM</code> clause contains the path prefix of one or more time series to be queried, and wildcards are supported.</li><li>When executing a query, the path prefix in the <code>FROM</code> clause and the suffix in the <code>SELECT</code> clause will be concatenated to obtain a complete query target time series.</li></ul><h4 id="where-clause" tabindex="-1"><a class="header-anchor" href="#where-clause"><span><code>WHERE</code> clause</span></a></h4><ul><li>The <code>WHERE</code> clause specifies the filtering conditions for data rows, consisting of a <code>whereCondition</code>.</li><li><code>whereCondition</code> is a logical expression that evaluates to true for each row to be selected. If there is no <code>WHERE</code> clause, all rows will be selected.</li><li>In <code>whereCondition</code>, any IOTDB-supported functions and operators can be used except aggregate functions.</li></ul><h4 id="group-by-clause" tabindex="-1"><a class="header-anchor" href="#group-by-clause"><span><code>GROUP BY</code> clause</span></a></h4><ul><li>The <code>GROUP BY</code> clause specifies how the time series are aggregated by segment or group.</li><li>Segmented aggregation refers to segmenting data in the row direction according to the time dimension, aiming at the time relationship between different data points in the same time series, and obtaining an aggregated value for each segment. Currently only <strong>group by time</strong>、<strong>group by variation</strong>、<strong>group by condition</strong>、<strong>group by session</strong> and <strong>group by count</strong> is supported, and more segmentation methods will be supported in the future.</li><li>Group aggregation refers to grouping the potential business attributes of time series for different time series. Each group contains several time series, and each group gets an aggregated value. Support <strong>group by path level</strong> and <strong>group by tag</strong> two grouping methods.</li><li>Segment aggregation and group aggregation can be mixed.</li></ul><h4 id="having-clause" tabindex="-1"><a class="header-anchor" href="#having-clause"><span><code>HAVING</code> clause</span></a></h4><ul><li>The <code>HAVING</code> clause specifies the filter conditions for the aggregation results, consisting of a <code>havingCondition</code>.</li><li><code>havingCondition</code> is a logical expression that evaluates to true for the aggregation results to be selected. If there is no <code>HAVING</code> clause, all aggregated results will be selected.</li><li><code>HAVING</code> is to be used with aggregate functions and the <code>GROUP BY</code> clause.</li></ul><h4 id="order-by-clause" tabindex="-1"><a class="header-anchor" href="#order-by-clause"><span><code>ORDER BY</code> clause</span></a></h4><ul><li>The <code>ORDER BY</code> clause is used to specify how the result set is sorted.</li><li>In ALIGN BY TIME mode: By default, they are sorted in ascending order of timestamp size, and <code>ORDER BY TIME DESC</code> can be used to specify that the result set is sorted in descending order of timestamp.</li><li>In ALIGN BY DEVICE mode: arrange according to the device first, and sort each device in ascending order according to the timestamp. The ordering and priority can be adjusted by <code>ORDER BY</code> clause.</li></ul><h4 id="fill-clause" tabindex="-1"><a class="header-anchor" href="#fill-clause"><span><code>FILL</code> clause</span></a></h4><ul><li>The <code>FILL</code> clause is used to specify the filling mode in the case of missing data, allowing users to fill in empty values ​​for the result set of any query according to a specific method.</li></ul><h4 id="slimit-and-soffset-clauses" tabindex="-1"><a class="header-anchor" href="#slimit-and-soffset-clauses"><span><code>SLIMIT</code> and <code>SOFFSET</code> clauses</span></a></h4><ul><li><code>SLIMIT</code> specifies the number of columns of the query result, and <code>SOFFSET</code> specifies the starting column position of the query result display. <code>SLIMIT</code> and <code>SOFFSET</code> are only used to control value columns and have no effect on time and device columns.</li></ul><h4 id="limit-and-offset-clauses" tabindex="-1"><a class="header-anchor" href="#limit-and-offset-clauses"><span><code>LIMIT</code> and <code>OFFSET</code> clauses</span></a></h4><ul><li><code>LIMIT</code> specifies the number of rows of the query result, and <code>OFFSET</code> specifies the starting row position of the query result display.</li></ul><h4 id="align-by-clause" tabindex="-1"><a class="header-anchor" href="#align-by-clause"><span><code>ALIGN BY</code> clause</span></a></h4><ul><li>The query result set is <strong>ALIGN BY TIME</strong> by default, including a time column and several value columns, and the timestamps of each column of data in each row are the same.</li><li>It also supports <strong>ALIGN BY DEVICE</strong>. The query result set contains a time column, a device column, and several value columns.</li></ul><h3 id="basic-examples" tabindex="-1"><a class="header-anchor" href="#basic-examples"><span>Basic Examples</span></a></h3><h4 id="select-a-column-of-data-based-on-a-time-interval" tabindex="-1"><a class="header-anchor" href="#select-a-column-of-data-based-on-a-time-interval"><span>Select a Column of Data Based on a Time Interval</span></a></h4><p>The SQL statement is:</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> temperature <span class="token keyword">from</span> root<span class="token punctuation">.</span>ln<span class="token punctuation">.</span>wf01<span class="token punctuation">.</span>wt01 <span class="token keyword">where</span> <span class="token keyword">time</span> <span class="token operator">&lt;</span> <span class="token number">2017</span><span class="token operator">-</span><span class="token number">11</span><span class="token operator">-</span><span class="token number">01</span>T00:<span class="token number">08</span>:<span class="token number">00.000</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>which means:</p><p>The selected device is ln group wf01 plant wt01 device; the selected timeseries is the temperature sensor (temperature). The SQL statement requires that all temperature sensor values before the time point of &quot;2017-11-01T00:08:00.000&quot; be selected.</p><p>The execution result of this SQL statement is as follows:</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>+-----------------------------+-----------------------------+
|                         Time|root.ln.wf01.wt01.temperature|
+-----------------------------+-----------------------------+
|2017-11-01T00:00:00.000+08:00|                        25.96|
|2017-11-01T00:01:00.000+08:00|                        24.36|
|2017-11-01T00:02:00.000+08:00|                        20.09|
|2017-11-01T00:03:00.000+08:00|                        20.18|
|2017-11-01T00:04:00.000+08:00|                        21.13|
|2017-11-01T00:05:00.000+08:00|                        22.72|
|2017-11-01T00:06:00.000+08:00|                        20.71|
|2017-11-01T00:07:00.000+08:00|                        21.45|
+-----------------------------+-----------------------------+
Total line number = 8
It costs 0.026s
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><h4 id="select-multiple-columns-of-data-based-on-a-time-interval" tabindex="-1"><a class="header-anchor" href="#select-multiple-columns-of-data-based-on-a-time-interval"><span>Select Multiple Columns of Data Based on a Time Interval</span></a></h4><p>The SQL statement is:</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> <span class="token keyword">status</span><span class="token punctuation">,</span> temperature <span class="token keyword">from</span> root<span class="token punctuation">.</span>ln<span class="token punctuation">.</span>wf01<span class="token punctuation">.</span>wt01 <span class="token keyword">where</span> <span class="token keyword">time</span> <span class="token operator">&gt;</span> <span class="token number">2017</span><span class="token operator">-</span><span class="token number">11</span><span class="token operator">-</span><span class="token number">01</span>T00:<span class="token number">05</span>:<span class="token number">00.000</span> <span class="token operator">and</span> <span class="token keyword">time</span> <span class="token operator">&lt;</span> <span class="token number">2017</span><span class="token operator">-</span><span class="token number">11</span><span class="token operator">-</span><span class="token number">01</span>T00:<span class="token number">12</span>:<span class="token number">00.000</span><span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>which means:</p><p>The selected device is ln group wf01 plant wt01 device; the selected timeseries is &quot;status&quot; and &quot;temperature&quot;. The SQL statement requires that the status and temperature sensor values between the time point of &quot;2017-11-01T00:05:00.000&quot; and &quot;2017-11-01T00:12:00.000&quot; be selected.</p><p>The execution result of this SQL statement is as follows:</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>+-----------------------------+------------------------+-----------------------------+
|                         Time|root.ln.wf01.wt01.status|root.ln.wf01.wt01.temperature|
+-----------------------------+------------------------+-----------------------------+
|2017-11-01T00:06:00.000+08:00|                   false|                        20.71|
|2017-11-01T00:07:00.000+08:00|                   false|                        21.45|
|2017-11-01T00:08:00.000+08:00|                   false|                        22.58|
|2017-11-01T00:09:00.000+08:00|                   false|                        20.98|
|2017-11-01T00:10:00.000+08:00|                    true|                        25.52|
|2017-11-01T00:11:00.000+08:00|                   false|                        22.91|
+-----------------------------+------------------------+-----------------------------+
Total line number = 6
It costs 0.018s
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><h4 id="select-multiple-columns-of-data-for-the-same-device-according-to-multiple-time-intervals" tabindex="-1"><a class="header-anchor" href="#select-multiple-columns-of-data-for-the-same-device-according-to-multiple-time-intervals"><span>Select Multiple Columns of Data for the Same Device According to Multiple Time Intervals</span></a></h4><p>IoTDB supports specifying multiple time interval conditions in a query. Users can combine time interval conditions at will according to their needs. For example, the SQL statement is:</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> <span class="token keyword">status</span><span class="token punctuation">,</span>temperature <span class="token keyword">from</span> root<span class="token punctuation">.</span>ln<span class="token punctuation">.</span>wf01<span class="token punctuation">.</span>wt01 <span class="token keyword">where</span> <span class="token punctuation">(</span><span class="token keyword">time</span> <span class="token operator">&gt;</span> <span class="token number">2017</span><span class="token operator">-</span><span class="token number">11</span><span class="token operator">-</span><span class="token number">01</span>T00:<span class="token number">05</span>:<span class="token number">00.000</span> <span class="token operator">and</span> <span class="token keyword">time</span> <span class="token operator">&lt;</span> <span class="token number">2017</span><span class="token operator">-</span><span class="token number">11</span><span class="token operator">-</span><span class="token number">01</span>T00:<span class="token number">12</span>:<span class="token number">00.000</span><span class="token punctuation">)</span> <span class="token operator">or</span> <span class="token punctuation">(</span><span class="token keyword">time</span> <span class="token operator">&gt;=</span> <span class="token number">2017</span><span class="token operator">-</span><span class="token number">11</span><span class="token operator">-</span><span class="token number">01</span>T16:<span class="token number">35</span>:<span class="token number">00.000</span> <span class="token operator">and</span> <span class="token keyword">time</span> <span class="token operator">&lt;=</span> <span class="token number">2017</span><span class="token operator">-</span><span class="token number">11</span><span class="token operator">-</span><span class="token number">01</span>T16:<span class="token number">37</span>:<span class="token number">00.000</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>which means:</p><p>The selected device is ln group wf01 plant wt01 device; the selected timeseries is &quot;status&quot; and &quot;temperature&quot;; the statement specifies two different time intervals, namely &quot;2017-11-01T00:05:00.000 to 2017-11-01T00:12:00.000&quot; and &quot;2017-11-01T16:35:00.000 to 2017-11-01T16:37:00.000&quot;. The SQL statement requires that the values of selected timeseries satisfying any time interval be selected.</p><p>The execution result of this SQL statement is as follows:</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>+-----------------------------+------------------------+-----------------------------+
|                         Time|root.ln.wf01.wt01.status|root.ln.wf01.wt01.temperature|
+-----------------------------+------------------------+-----------------------------+
|2017-11-01T00:06:00.000+08:00|                   false|                        20.71|
|2017-11-01T00:07:00.000+08:00|                   false|                        21.45|
|2017-11-01T00:08:00.000+08:00|                   false|                        22.58|
|2017-11-01T00:09:00.000+08:00|                   false|                        20.98|
|2017-11-01T00:10:00.000+08:00|                    true|                        25.52|
|2017-11-01T00:11:00.000+08:00|                   false|                        22.91|
|2017-11-01T16:35:00.000+08:00|                    true|                        23.44|
|2017-11-01T16:36:00.000+08:00|                   false|                        21.98|
|2017-11-01T16:37:00.000+08:00|                   false|                        21.93|
+-----------------------------+------------------------+-----------------------------+
Total line number = 9
It costs 0.018s
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><h4 id="choose-multiple-columns-of-data-for-different-devices-according-to-multiple-time-intervals" tabindex="-1"><a class="header-anchor" href="#choose-multiple-columns-of-data-for-different-devices-according-to-multiple-time-intervals"><span>Choose Multiple Columns of Data for Different Devices According to Multiple Time Intervals</span></a></h4><p>The system supports the selection of data in any column in a query, i.e., the selected columns can come from different devices. For example, the SQL statement is:</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> wf01<span class="token punctuation">.</span>wt01<span class="token punctuation">.</span><span class="token keyword">status</span><span class="token punctuation">,</span>wf02<span class="token punctuation">.</span>wt02<span class="token punctuation">.</span>hardware <span class="token keyword">from</span> root<span class="token punctuation">.</span>ln <span class="token keyword">where</span> <span class="token punctuation">(</span><span class="token keyword">time</span> <span class="token operator">&gt;</span> <span class="token number">2017</span><span class="token operator">-</span><span class="token number">11</span><span class="token operator">-</span><span class="token number">01</span>T00:<span class="token number">05</span>:<span class="token number">00.000</span> <span class="token operator">and</span> <span class="token keyword">time</span> <span class="token operator">&lt;</span> <span class="token number">2017</span><span class="token operator">-</span><span class="token number">11</span><span class="token operator">-</span><span class="token number">01</span>T00:<span class="token number">12</span>:<span class="token number">00.000</span><span class="token punctuation">)</span> <span class="token operator">or</span> <span class="token punctuation">(</span><span class="token keyword">time</span> <span class="token operator">&gt;=</span> <span class="token number">2017</span><span class="token operator">-</span><span class="token number">11</span><span class="token operator">-</span><span class="token number">01</span>T16:<span class="token number">35</span>:<span class="token number">00.000</span> <span class="token operator">and</span> <span class="token keyword">time</span> <span class="token operator">&lt;=</span> <span class="token number">2017</span><span class="token operator">-</span><span class="token number">11</span><span class="token operator">-</span><span class="token number">01</span>T16:<span class="token number">37</span>:<span class="token number">00.000</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>which means:</p><p>The selected timeseries are &quot;the power supply status of ln group wf01 plant wt01 device&quot; and &quot;the hardware version of ln group wf02 plant wt02 device&quot;; the statement specifies two different time intervals, namely &quot;2017-11-01T00:05:00.000 to 2017-11-01T00:12:00.000&quot; and &quot;2017-11-01T16:35:00.000 to 2017-11-01T16:37:00.000&quot;. The SQL statement requires that the values of selected timeseries satisfying any time interval be selected.</p><p>The execution result of this SQL statement is as follows:</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>+-----------------------------+------------------------+--------------------------+
|                         Time|root.ln.wf01.wt01.status|root.ln.wf02.wt02.hardware|
+-----------------------------+------------------------+--------------------------+
|2017-11-01T00:06:00.000+08:00|                   false|                        v1|
|2017-11-01T00:07:00.000+08:00|                   false|                        v1|
|2017-11-01T00:08:00.000+08:00|                   false|                        v1|
|2017-11-01T00:09:00.000+08:00|                   false|                        v1|
|2017-11-01T00:10:00.000+08:00|                    true|                        v2|
|2017-11-01T00:11:00.000+08:00|                   false|                        v1|
|2017-11-01T16:35:00.000+08:00|                    true|                        v2|
|2017-11-01T16:36:00.000+08:00|                   false|                        v1|
|2017-11-01T16:37:00.000+08:00|                   false|                        v1|
+-----------------------------+------------------------+--------------------------+
Total line number = 9
It costs 0.014s
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><h4 id="order-by-time-query" tabindex="-1"><a class="header-anchor" href="#order-by-time-query"><span>Order By Time Query</span></a></h4><p>IoTDB supports the &#39;order by time&#39; statement since 0.11, it&#39;s used to display results in descending order by time.<br> For example, the SQL statement is:</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> <span class="token operator">*</span> <span class="token keyword">from</span> root<span class="token punctuation">.</span>ln<span class="token punctuation">.</span><span class="token operator">*</span><span class="token operator">*</span> <span class="token keyword">where</span> <span class="token keyword">time</span> <span class="token operator">&gt;</span> <span class="token number">1</span> <span class="token keyword">order</span> <span class="token keyword">by</span> <span class="token keyword">time</span> <span class="token keyword">desc</span> <span class="token keyword">limit</span> <span class="token number">10</span><span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>The execution result of this SQL statement is as follows:</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>+-----------------------------+--------------------------+------------------------+-----------------------------+------------------------+
|                         Time|root.ln.wf02.wt02.hardware|root.ln.wf02.wt02.status|root.ln.wf01.wt01.temperature|root.ln.wf01.wt01.status|
+-----------------------------+--------------------------+------------------------+-----------------------------+------------------------+
|2017-11-07T23:59:00.000+08:00|                        v1|                   false|                        21.07|                   false|
|2017-11-07T23:58:00.000+08:00|                        v1|                   false|                        22.93|                   false|
|2017-11-07T23:57:00.000+08:00|                        v2|                    true|                        24.39|                    true|
|2017-11-07T23:56:00.000+08:00|                        v2|                    true|                        24.44|                    true|
|2017-11-07T23:55:00.000+08:00|                        v2|                    true|                         25.9|                    true|
|2017-11-07T23:54:00.000+08:00|                        v1|                   false|                        22.52|                   false|
|2017-11-07T23:53:00.000+08:00|                        v2|                    true|                        24.58|                    true|
|2017-11-07T23:52:00.000+08:00|                        v1|                   false|                        20.18|                   false|
|2017-11-07T23:51:00.000+08:00|                        v1|                   false|                        22.24|                   false|
|2017-11-07T23:50:00.000+08:00|                        v2|                    true|                         23.7|                    true|
+-----------------------------+--------------------------+------------------------+-----------------------------+------------------------+
Total line number = 10
It costs 0.016s
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><h3 id="execution-interface" tabindex="-1"><a class="header-anchor" href="#execution-interface"><span>Execution Interface</span></a></h3><p>In IoTDB, there are two ways to execute data query:</p><ul><li>Execute queries using IoTDB-SQL.</li><li>Efficient execution interfaces for common queries, including time-series raw data query, last query, and aggregation query.</li></ul><h4 id="execute-queries-using-iotdb-sql" tabindex="-1"><a class="header-anchor" href="#execute-queries-using-iotdb-sql"><span>Execute queries using IoTDB-SQL</span></a></h4><p>Data query statements can be used in SQL command-line terminals, JDBC, JAVA / C++ / Python / Go and other native APIs, and RESTful APIs.</p><ul><li><p>Execute the query statement in the SQL command line terminal: start the SQL command line terminal, and directly enter the query statement to execute, see <a class="route-link" href="/UserGuide/V1.2.x/Tools-System/CLI.html">SQL command line terminal</a>.</p></li><li><p>Execute query statements in JDBC, see <a class="route-link" href="/UserGuide/V1.2.x/API/Programming-JDBC.html">JDBC</a> for details.</p></li><li><p>Execute query statements in native APIs such as JAVA / C++ / Python / Go. For details, please refer to the relevant documentation in the Application Programming Interface chapter. The interface prototype is as follows:</p><div class="language-java line-numbers-mode" data-ext="java" data-title="java"><pre class="language-java"><code><span class="token class-name">SessionDataSet</span> <span class="token function">executeQueryStatement</span><span class="token punctuation">(</span><span class="token class-name">String</span> sql<span class="token punctuation">)</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div></li><li><p>Used in RESTful API, see <a class="route-link" href="/UserGuide/V1.2.x/API/RestServiceV1.html">HTTP API V1</a> or <a class="route-link" href="/UserGuide/V1.2.x/API/RestServiceV2.html">HTTP API V2</a> for details.</p></li></ul><h4 id="efficient-execution-interfaces" tabindex="-1"><a class="header-anchor" href="#efficient-execution-interfaces"><span>Efficient execution interfaces</span></a></h4><p>The native APIs provide efficient execution interfaces for commonly used queries, which can save time-consuming operations such as SQL parsing. include:</p><ul><li>Time-series raw data query with time range: <ul><li>The specified query time range is a left-closed right-open interval, including the start time but excluding the end time.</li></ul></li></ul><div class="language-java line-numbers-mode" data-ext="java" data-title="java"><pre class="language-java"><code><span class="token class-name">SessionDataSet</span> <span class="token function">executeRawDataQuery</span><span class="token punctuation">(</span><span class="token class-name">List</span><span class="token generics"><span class="token punctuation">&lt;</span><span class="token class-name">String</span><span class="token punctuation">&gt;</span></span> paths<span class="token punctuation">,</span> <span class="token keyword">long</span> startTime<span class="token punctuation">,</span> <span class="token keyword">long</span> endTime<span class="token punctuation">)</span><span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><ul><li>Last query: <ul><li>Query the last data, whose timestamp is greater than or equal LastTime.</li></ul></li></ul><div class="language-java line-numbers-mode" data-ext="java" data-title="java"><pre class="language-java"><code><span class="token class-name">SessionDataSet</span> <span class="token function">executeLastDataQuery</span><span class="token punctuation">(</span><span class="token class-name">List</span><span class="token generics"><span class="token punctuation">&lt;</span><span class="token class-name">String</span><span class="token punctuation">&gt;</span></span> paths<span class="token punctuation">,</span> <span class="token keyword">long</span> <span class="token class-name">LastTime</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><ul><li>Aggregation query: <ul><li>Support specified query time range: The specified query time range is a left-closed right-open interval, including the start time but not the end time.</li><li>Support GROUP BY TIME.</li></ul></li></ul><div class="language-java line-numbers-mode" data-ext="java" data-title="java"><pre class="language-java"><code><span class="token class-name">SessionDataSet</span> <span class="token function">executeAggregationQuery</span><span class="token punctuation">(</span><span class="token class-name">List</span><span class="token generics"><span class="token punctuation">&lt;</span><span class="token class-name">String</span><span class="token punctuation">&gt;</span></span> paths<span class="token punctuation">,</span> <span class="token class-name">List</span><span class="token generics"><span class="token punctuation">&lt;</span><span class="token class-name">Aggregation</span><span class="token punctuation">&gt;</span></span> aggregations<span class="token punctuation">)</span><span class="token punctuation">;</span>

<span class="token class-name">SessionDataSet</span> <span class="token function">executeAggregationQuery</span><span class="token punctuation">(</span>
    <span class="token class-name">List</span><span class="token generics"><span class="token punctuation">&lt;</span><span class="token class-name">String</span><span class="token punctuation">&gt;</span></span> paths<span class="token punctuation">,</span> <span class="token class-name">List</span><span class="token generics"><span class="token punctuation">&lt;</span><span class="token class-name">Aggregation</span><span class="token punctuation">&gt;</span></span> aggregations<span class="token punctuation">,</span> <span class="token keyword">long</span> startTime<span class="token punctuation">,</span> <span class="token keyword">long</span> endTime<span class="token punctuation">)</span><span class="token punctuation">;</span>

<span class="token class-name">SessionDataSet</span> <span class="token function">executeAggregationQuery</span><span class="token punctuation">(</span>
    <span class="token class-name">List</span><span class="token generics"><span class="token punctuation">&lt;</span><span class="token class-name">String</span><span class="token punctuation">&gt;</span></span> paths<span class="token punctuation">,</span>
    <span class="token class-name">List</span><span class="token generics"><span class="token punctuation">&lt;</span><span class="token class-name">Aggregation</span><span class="token punctuation">&gt;</span></span> aggregations<span class="token punctuation">,</span>
    <span class="token keyword">long</span> startTime<span class="token punctuation">,</span>
    <span class="token keyword">long</span> endTime<span class="token punctuation">,</span>
    <span class="token keyword">long</span> interval<span class="token punctuation">)</span><span class="token punctuation">;</span>

<span class="token class-name">SessionDataSet</span> <span class="token function">executeAggregationQuery</span><span class="token punctuation">(</span>
    <span class="token class-name">List</span><span class="token generics"><span class="token punctuation">&lt;</span><span class="token class-name">String</span><span class="token punctuation">&gt;</span></span> paths<span class="token punctuation">,</span>
    <span class="token class-name">List</span><span class="token generics"><span class="token punctuation">&lt;</span><span class="token class-name">Aggregation</span><span class="token punctuation">&gt;</span></span> aggregations<span class="token punctuation">,</span>
    <span class="token keyword">long</span> startTime<span class="token punctuation">,</span>
    <span class="token keyword">long</span> endTime<span class="token punctuation">,</span>
    <span class="token keyword">long</span> interval<span class="token punctuation">,</span>
    <span class="token keyword">long</span> slidingStep<span class="token punctuation">)</span><span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><h2 id="select-clause-1" tabindex="-1"><a class="header-anchor" href="#select-clause-1"><span><code>SELECT</code> CLAUSE</span></a></h2><p>The <code>SELECT</code> clause specifies the output of the query, consisting of several <code>selectExpr</code>. Each <code>selectExpr</code> defines one or more columns in the query result. For select expression details, see document <a class="route-link" href="/UserGuide/V1.2.x/User-Manual/Operator-and-Expression.html">Operator-and-Expression</a>.</p><ul><li>Example 1:</li></ul><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> temperature <span class="token keyword">from</span> root<span class="token punctuation">.</span>ln<span class="token punctuation">.</span>wf01<span class="token punctuation">.</span>wt01 
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><ul><li>Example 2:</li></ul><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> <span class="token keyword">status</span><span class="token punctuation">,</span> temperature <span class="token keyword">from</span> root<span class="token punctuation">.</span>ln<span class="token punctuation">.</span>wf01<span class="token punctuation">.</span>wt01
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><h3 id="last-query" tabindex="-1"><a class="header-anchor" href="#last-query"><span>Last Query</span></a></h3><p>The last query is a special type of query in Apache IoTDB. It returns the data point with the largest timestamp of the specified time series. In other word, it returns the latest state of a time series. This feature is especially important in IoT data analysis scenarios. To meet the performance requirement of real-time device monitoring systems, Apache IoTDB caches the latest values of all time series to achieve microsecond read latency.</p><p>The last query is to return the most recent data point of the given timeseries in a three column format.</p><p>The SQL syntax is defined as:</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> <span class="token keyword">last</span> <span class="token operator">&lt;</span>Path<span class="token operator">&gt;</span> <span class="token punctuation">[</span>COMMA <span class="token operator">&lt;</span>Path<span class="token operator">&gt;</span><span class="token punctuation">]</span><span class="token operator">*</span> <span class="token keyword">from</span> <span class="token operator">&lt;</span> PrefixPath <span class="token operator">&gt;</span> <span class="token punctuation">[</span>COMMA <span class="token operator">&lt;</span> PrefixPath <span class="token operator">&gt;</span><span class="token punctuation">]</span><span class="token operator">*</span> <span class="token operator">&lt;</span>WhereClause<span class="token operator">&gt;</span> <span class="token punctuation">[</span><span class="token keyword">ORDER</span> <span class="token keyword">BY</span> TIMESERIES <span class="token punctuation">(</span><span class="token keyword">DESC</span> <span class="token operator">|</span> <span class="token keyword">ASC</span><span class="token punctuation">)</span>?<span class="token punctuation">]</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>which means: Query and return the last data points of timeseries prefixPath.path.</p><ul><li><p>Only time filter is supported in &lt;WhereClause&gt;. Any other filters given in the &lt;WhereClause&gt; will give an exception. When the cached most recent data point does not satisfy the criterion specified by the filter, IoTDB will have to get the result from the external storage, which may cause a decrease in performance.</p></li><li><p>The result will be returned in a four column table format.</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>| Time | timeseries | value | dataType |
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p><strong>Note:</strong> The <code>value</code> colum will always return the value as <code>string</code> and thus also has <code>TSDataType.TEXT</code>. Therefore, the column <code>dataType</code> is returned also which contains the <em>real</em> type how the value should be interpreted.</p></li><li><p>We can use <code>TIME/TIMESERIES/VALUE/DATATYPE (DESC | ASC)</code> to specify that the result set is sorted in descending/ascending order based on a particular column. When the value column contains multiple types of data, the sorting is based on the string representation of the values.</p></li></ul><p><strong>Example 1:</strong> get the last point of root.ln.wf01.wt01.status:</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>IoTDB&gt; select last status from root.ln.wf01.wt01
+-----------------------------+------------------------+-----+--------+
|                         Time|              timeseries|value|dataType|
+-----------------------------+------------------------+-----+--------+
|2017-11-07T23:59:00.000+08:00|root.ln.wf01.wt01.status|false| BOOLEAN|
+-----------------------------+------------------------+-----+--------+
Total line number = 1
It costs 0.000s
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p><strong>Example 2:</strong> get the last status and temperature points of root.ln.wf01.wt01, whose timestamp larger or equal to 2017-11-07T23:50:00。</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>IoTDB&gt; select last status, temperature from root.ln.wf01.wt01 where time &gt;= 2017-11-07T23:50:00
+-----------------------------+-----------------------------+---------+--------+
|                         Time|                   timeseries|    value|dataType|
+-----------------------------+-----------------------------+---------+--------+
|2017-11-07T23:59:00.000+08:00|     root.ln.wf01.wt01.status|    false| BOOLEAN|
|2017-11-07T23:59:00.000+08:00|root.ln.wf01.wt01.temperature|21.067368|  DOUBLE|
+-----------------------------+-----------------------------+---------+--------+
Total line number = 2
It costs 0.002s
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p><strong>Example 3:</strong> get the last points of all sensor in root.ln.wf01.wt01, and order the result by the timeseries column in descending order</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>IoTDB&gt; select last * from root.ln.wf01.wt01 order by timeseries desc;
+-----------------------------+-----------------------------+---------+--------+
|                         Time|                   timeseries|    value|dataType|
+-----------------------------+-----------------------------+---------+--------+
|2017-11-07T23:59:00.000+08:00|root.ln.wf01.wt01.temperature|21.067368|  DOUBLE|
|2017-11-07T23:59:00.000+08:00|     root.ln.wf01.wt01.status|    false| BOOLEAN|
+-----------------------------+-----------------------------+---------+--------+
Total line number = 2
It costs 0.002s
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p><strong>Example 4：</strong> get the last points of all sensor in root.ln.wf01.wt01, and order the result by the dataType column in descending order</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>IoTDB&gt; select last * from root.ln.wf01.wt01 order by dataType desc;
+-----------------------------+-----------------------------+---------+--------+
|                         Time|                   timeseries|    value|dataType|
+-----------------------------+-----------------------------+---------+--------+
|2017-11-07T23:59:00.000+08:00|root.ln.wf01.wt01.temperature|21.067368|  DOUBLE|
|2017-11-07T23:59:00.000+08:00|     root.ln.wf01.wt01.status|    false| BOOLEAN|
+-----------------------------+-----------------------------+---------+--------+
Total line number = 2
It costs 0.002s
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><h2 id="where-clause-1" tabindex="-1"><a class="header-anchor" href="#where-clause-1"><span><code>WHERE</code> CLAUSE</span></a></h2><p>In IoTDB query statements, two filter conditions, <strong>time filter</strong> and <strong>value filter</strong>, are supported.</p><p>The supported operators are as follows:</p><ul><li>Comparison operators: greater than (<code>&gt;</code>), greater than or equal ( <code>&gt;=</code>), equal ( <code>=</code> or <code>==</code>), not equal ( <code>!=</code> or <code>&lt;&gt;</code>), less than or equal ( <code>&lt;=</code>), less than ( <code>&lt;</code>).</li><li>Logical operators: and ( <code>AND</code> or <code>&amp;</code> or <code>&amp;&amp;</code>), or ( <code>OR</code> or <code>|</code> or <code>||</code>), not ( <code>NOT</code> or <code>!</code>).</li><li>Range contains operator: contains ( <code>IN</code> ).</li><li>String matches operator: <code>LIKE</code>, <code>REGEXP</code>.</li></ul><h3 id="time-filter" tabindex="-1"><a class="header-anchor" href="#time-filter"><span>Time Filter</span></a></h3><p>Use time filters to filter data for a specific time range. For supported formats of timestamps, please refer to <a class="route-link" href="/UserGuide/V1.2.x/Basic-Concept/Data-Type.html">Timestamp</a> .</p><p>An example is as follows:</p><ol><li><p>Select data with timestamp greater than 2022-01-01T00:05:00.000:</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> s1 <span class="token keyword">from</span> root<span class="token punctuation">.</span>sg1<span class="token punctuation">.</span>d1 <span class="token keyword">where</span> <span class="token keyword">time</span> <span class="token operator">&gt;</span> <span class="token number">2022</span><span class="token operator">-</span><span class="token number">01</span><span class="token operator">-</span><span class="token number">01</span>T00:<span class="token number">05</span>:<span class="token number">00.000</span><span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div></li><li><p>Select data with timestamp equal to 2022-01-01T00:05:00.000:</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> s1 <span class="token keyword">from</span> root<span class="token punctuation">.</span>sg1<span class="token punctuation">.</span>d1 <span class="token keyword">where</span> <span class="token keyword">time</span> <span class="token operator">=</span> <span class="token number">2022</span><span class="token operator">-</span><span class="token number">01</span><span class="token operator">-</span><span class="token number">01</span>T00:<span class="token number">05</span>:<span class="token number">00.000</span><span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div></li><li><p>Select the data in the time interval [2017-11-01T00:05:00.000, 2017-11-01T00:12:00.000):</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> s1 <span class="token keyword">from</span> root<span class="token punctuation">.</span>sg1<span class="token punctuation">.</span>d1 <span class="token keyword">where</span> <span class="token keyword">time</span> <span class="token operator">&gt;=</span> <span class="token number">2022</span><span class="token operator">-</span><span class="token number">01</span><span class="token operator">-</span><span class="token number">01</span>T00:<span class="token number">05</span>:<span class="token number">00.000</span> <span class="token operator">and</span> <span class="token keyword">time</span> <span class="token operator">&lt;</span> <span class="token number">2017</span><span class="token operator">-</span><span class="token number">11</span><span class="token operator">-</span><span class="token number">01</span>T00:<span class="token number">12</span>:<span class="token number">00.000</span><span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div></li></ol><p>Note: In the above example, <code>time</code> can also be written as <code>timestamp</code>.</p><h3 id="value-filter" tabindex="-1"><a class="header-anchor" href="#value-filter"><span>Value Filter</span></a></h3><p>Use value filters to filter data whose data values meet certain criteria. <strong>Allow</strong> to use a time series not selected in the select clause as a value filter.</p><p>An example is as follows:</p><ol><li><p>Select data with a value greater than 36.5:</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> temperature <span class="token keyword">from</span> root<span class="token punctuation">.</span>sg1<span class="token punctuation">.</span>d1 <span class="token keyword">where</span> temperature <span class="token operator">&gt;</span> <span class="token number">36.5</span><span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div></li><li><p>Select data with value equal to true:</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> <span class="token keyword">status</span> <span class="token keyword">from</span> root<span class="token punctuation">.</span>sg1<span class="token punctuation">.</span>d1 <span class="token keyword">where</span> <span class="token keyword">status</span> <span class="token operator">=</span> <span class="token boolean">true</span><span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div></li><li><p>Select data for the interval [36.5,40] or not:</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> temperature <span class="token keyword">from</span> root<span class="token punctuation">.</span>sg1<span class="token punctuation">.</span>d1 <span class="token keyword">where</span> temperature <span class="token operator">between</span> <span class="token number">36.5</span> <span class="token operator">and</span> <span class="token number">40</span><span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> temperature <span class="token keyword">from</span> root<span class="token punctuation">.</span>sg1<span class="token punctuation">.</span>d1 <span class="token keyword">where</span> temperature <span class="token operator">not</span> <span class="token operator">between</span> <span class="token number">36.5</span> <span class="token operator">and</span> <span class="token number">40</span><span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div></li><li><p>Select data with values within a specific range:</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> code <span class="token keyword">from</span> root<span class="token punctuation">.</span>sg1<span class="token punctuation">.</span>d1 <span class="token keyword">where</span> code <span class="token operator">in</span> <span class="token punctuation">(</span><span class="token string">&#39;200&#39;</span><span class="token punctuation">,</span> <span class="token string">&#39;300&#39;</span><span class="token punctuation">,</span> <span class="token string">&#39;400&#39;</span><span class="token punctuation">,</span> <span class="token string">&#39;500&#39;</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div></li><li><p>Select data with values outside a certain range:</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> code <span class="token keyword">from</span> root<span class="token punctuation">.</span>sg1<span class="token punctuation">.</span>d1 <span class="token keyword">where</span> code <span class="token operator">not</span> <span class="token operator">in</span> <span class="token punctuation">(</span><span class="token string">&#39;200&#39;</span><span class="token punctuation">,</span> <span class="token string">&#39;300&#39;</span><span class="token punctuation">,</span> <span class="token string">&#39;400&#39;</span><span class="token punctuation">,</span> <span class="token string">&#39;500&#39;</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div></li><li><p>Select data with values is null:</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> code <span class="token keyword">from</span> root<span class="token punctuation">.</span>sg1<span class="token punctuation">.</span>d1 <span class="token keyword">where</span> temperature <span class="token operator">is</span> <span class="token boolean">null</span><span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div></li><li><p>Select data with values is not null:</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> code <span class="token keyword">from</span> root<span class="token punctuation">.</span>sg1<span class="token punctuation">.</span>d1 <span class="token keyword">where</span> temperature <span class="token operator">is</span> <span class="token operator">not</span> <span class="token boolean">null</span><span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div></li></ol><h3 id="fuzzy-query" tabindex="-1"><a class="header-anchor" href="#fuzzy-query"><span>Fuzzy Query</span></a></h3><p>Fuzzy query is divided into Like statement and Regexp statement, both of which can support fuzzy matching of TEXT type data.</p><p>Like statement:</p><h4 id="fuzzy-matching-using-like" tabindex="-1"><a class="header-anchor" href="#fuzzy-matching-using-like"><span>Fuzzy matching using <code>Like</code></span></a></h4><p>In the value filter condition, for TEXT type data, use <code>Like</code> and <code>Regexp</code> operators to perform fuzzy matching on data.</p><p><strong>Matching rules:</strong></p><ul><li>The percentage (<code>%</code>) wildcard matches any string of zero or more characters.</li><li>The underscore (<code>_</code>) wildcard matches any single character.</li></ul><p><strong>Example 1:</strong> Query data containing <code>&#39;cc&#39;</code> in <code>value</code> under <code>root.sg.d1</code>.</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>IoTDB&gt; select * from root.sg.d1 where value like &#39;%cc%&#39;
+-----------------------------+----------------+
|                         Time|root.sg.d1.value|
+-----------------------------+----------------+
|2017-11-01T00:00:00.000+08:00|        aabbccdd| 
|2017-11-01T00:00:01.000+08:00|              cc|
+-----------------------------+----------------+
Total line number = 2
It costs 0.002s
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p><strong>Example 2:</strong> Query data that consists of 3 characters and the second character is <code>&#39;b&#39;</code> in <code>value</code> under <code>root.sg.d1</code>.</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>IoTDB&gt; select * from root.sg.device where value like &#39;_b_&#39;
+-----------------------------+----------------+
|                         Time|root.sg.d1.value|
+-----------------------------+----------------+
|2017-11-01T00:00:02.000+08:00|             abc| 
+-----------------------------+----------------+
Total line number = 1
It costs 0.002s
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><h4 id="fuzzy-matching-using-regexp" tabindex="-1"><a class="header-anchor" href="#fuzzy-matching-using-regexp"><span>Fuzzy matching using <code>Regexp</code></span></a></h4><p>The filter conditions that need to be passed in are regular expressions in the Java standard library style.</p><p><strong>Examples of common regular matching:</strong></p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>All characters with a length of 3-20: ^.{3,20}$
Uppercase english characters: ^[A-Z]+$
Numbers and English characters: ^[A-Za-z0-9]+$
Beginning with a: ^a.*
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p><strong>Example 1:</strong> Query a string composed of 26 English characters for the value under root.sg.d1</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>IoTDB&gt; select * from root.sg.d1 where value regexp &#39;^[A-Za-z]+$&#39;
+-----------------------------+----------------+
|                         Time|root.sg.d1.value|
+-----------------------------+----------------+
|2017-11-01T00:00:00.000+08:00|        aabbccdd| 
|2017-11-01T00:00:01.000+08:00|              cc|
+-----------------------------+----------------+
Total line number = 2
It costs 0.002s
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p><strong>Example 2:</strong> Query root.sg.d1 where the value value is a string composed of 26 lowercase English characters and the time is greater than 100</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>IoTDB&gt; select * from root.sg.d1 where value regexp &#39;^[a-z]+$&#39; and time &gt; 100
+-----------------------------+----------------+
|                         Time|root.sg.d1.value|
+-----------------------------+----------------+
|2017-11-01T00:00:00.000+08:00|        aabbccdd| 
|2017-11-01T00:00:01.000+08:00|              cc|
+-----------------------------+----------------+
Total line number = 2
It costs 0.002s
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><h2 id="group-by-clause-1" tabindex="-1"><a class="header-anchor" href="#group-by-clause-1"><span><code>GROUP BY</code> CLAUSE</span></a></h2><p>IoTDB supports using <code>GROUP BY</code> clause to aggregate the time series by segment and group.</p><p>Segmented aggregation refers to segmenting data in the row direction according to the time dimension, aiming at the time relationship between different data points in the same time series, and obtaining an aggregated value for each segment. Currently only <strong>group by time</strong>、<strong>group by variation</strong>、<strong>group by condition</strong>、<strong>group by session</strong> and <strong>group by count</strong> is supported, and more segmentation methods will be supported in the future.</p><p>Group aggregation refers to grouping the potential business attributes of time series for different time series. Each group contains several time series, and each group gets an aggregated value. Support <strong>group by path level</strong> and <strong>group by tag</strong> two grouping methods.</p><h3 id="aggregate-by-segment" tabindex="-1"><a class="header-anchor" href="#aggregate-by-segment"><span>Aggregate By Segment</span></a></h3><h4 id="aggregate-by-time" tabindex="-1"><a class="header-anchor" href="#aggregate-by-time"><span>Aggregate By Time</span></a></h4><p>Aggregate by time is a typical query method for time series data. Data is collected at high frequency and needs to be aggregated and calculated at certain time intervals. For example, to calculate the daily average temperature, the sequence of temperature needs to be segmented by day, and then calculated. average value.</p><p>Aggregate by time refers to a query method that uses a lower frequency than the time frequency of data collection, and is a special case of segmented aggregation. For example, the frequency of data collection is one second. If you want to display the data in one minute, you need to use time aggregagtion.</p><p>This section mainly introduces the related examples of time aggregation, using the <code>GROUP BY</code> clause. IoTDB supports partitioning result sets according to time interval and customized sliding step. And by default results are sorted by time in ascending order.</p><p>The GROUP BY statement provides users with three types of specified parameters:</p><ul><li>Parameter 1: The display window on the time axis</li><li>Parameter 2: Time interval for dividing the time axis(should be positive)</li><li>Parameter 3: Time sliding step (optional and defaults to equal the time interval if not set)</li></ul><p>The actual meanings of the three types of parameters are shown in Figure below.<br> Among them, the parameter 3 is optional.</p><center><img style="width:100%;max-width:800px;max-height:600px;margin-left:auto;margin-right:auto;display:block;" src="https://alioss.timecho.com/docs/img/github/69109512-f808bc80-0ab2-11ea-9e4d-b2b2f58fb474.png"></center><p>There are three typical examples of frequency reduction aggregation:</p><h5 id="aggregate-by-time-without-specifying-the-sliding-step-length" tabindex="-1"><a class="header-anchor" href="#aggregate-by-time-without-specifying-the-sliding-step-length"><span>Aggregate By Time without Specifying the Sliding Step Length</span></a></h5><p>The SQL statement is:</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> <span class="token function">count</span><span class="token punctuation">(</span><span class="token keyword">status</span><span class="token punctuation">)</span><span class="token punctuation">,</span> max_value<span class="token punctuation">(</span>temperature<span class="token punctuation">)</span> <span class="token keyword">from</span> root<span class="token punctuation">.</span>ln<span class="token punctuation">.</span>wf01<span class="token punctuation">.</span>wt01 <span class="token keyword">group</span> <span class="token keyword">by</span> <span class="token punctuation">(</span><span class="token punctuation">[</span><span class="token number">2017</span><span class="token operator">-</span><span class="token number">11</span><span class="token operator">-</span><span class="token number">01</span>T00:<span class="token number">00</span>:<span class="token number">00</span><span class="token punctuation">,</span> <span class="token number">2017</span><span class="token operator">-</span><span class="token number">11</span><span class="token operator">-</span><span class="token number">07</span>T23:<span class="token number">00</span>:<span class="token number">00</span><span class="token punctuation">)</span><span class="token punctuation">,</span><span class="token number">1</span>d<span class="token punctuation">)</span><span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>which means:</p><p>Since the sliding step length is not specified, the <code>GROUP BY</code> statement by default set the sliding step the same as the time interval which is <code>1d</code>.</p><p>The fist parameter of the <code>GROUP BY</code> statement above is the display window parameter, which determines the final display range is [2017-11-01T00:00:00, 2017-11-07T23:00:00).</p><p>The second parameter of the <code>GROUP BY</code> statement above is the time interval for dividing the time axis. Taking this parameter (1d) as time interval and startTime of the display window as the dividing origin, the time axis is divided into several continuous intervals, which are [0,1d), [1d, 2d), [2d, 3d), etc.</p><p>Then the system will use the time and value filtering condition in the <code>WHERE</code> clause and the first parameter of the <code>GROUP BY</code> statement as the data filtering condition to obtain the data satisfying the filtering condition (which in this case is the data in the range of [2017-11-01T00:00:00, 2017-11-07 T23:00:00]), and map these data to the previously segmented time axis (in this case there are mapped data in every 1-day period from 2017-11-01T00:00:00 to 2017-11-07T23:00:00:00).</p><p>Since there is data for each time period in the result range to be displayed, the execution result of the SQL statement is shown below:</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>+-----------------------------+-------------------------------+----------------------------------------+
|                         Time|count(root.ln.wf01.wt01.status)|max_value(root.ln.wf01.wt01.temperature)|
+-----------------------------+-------------------------------+----------------------------------------+
|2017-11-01T00:00:00.000+08:00|                           1440|                                    26.0|
|2017-11-02T00:00:00.000+08:00|                           1440|                                    26.0|
|2017-11-03T00:00:00.000+08:00|                           1440|                                   25.99|
|2017-11-04T00:00:00.000+08:00|                           1440|                                    26.0|
|2017-11-05T00:00:00.000+08:00|                           1440|                                    26.0|
|2017-11-06T00:00:00.000+08:00|                           1440|                                   25.99|
|2017-11-07T00:00:00.000+08:00|                           1380|                                    26.0|
+-----------------------------+-------------------------------+----------------------------------------+
Total line number = 7
It costs 0.024s
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><h5 id="aggregate-by-time-specifying-the-sliding-step-length" tabindex="-1"><a class="header-anchor" href="#aggregate-by-time-specifying-the-sliding-step-length"><span>Aggregate By Time Specifying the Sliding Step Length</span></a></h5><p>The SQL statement is:</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> <span class="token function">count</span><span class="token punctuation">(</span><span class="token keyword">status</span><span class="token punctuation">)</span><span class="token punctuation">,</span> max_value<span class="token punctuation">(</span>temperature<span class="token punctuation">)</span> <span class="token keyword">from</span> root<span class="token punctuation">.</span>ln<span class="token punctuation">.</span>wf01<span class="token punctuation">.</span>wt01 <span class="token keyword">group</span> <span class="token keyword">by</span> <span class="token punctuation">(</span><span class="token punctuation">[</span><span class="token number">2017</span><span class="token operator">-</span><span class="token number">11</span><span class="token operator">-</span><span class="token number">01</span> <span class="token number">00</span>:<span class="token number">00</span>:<span class="token number">00</span><span class="token punctuation">,</span> <span class="token number">2017</span><span class="token operator">-</span><span class="token number">11</span><span class="token operator">-</span><span class="token number">07</span> <span class="token number">23</span>:<span class="token number">00</span>:<span class="token number">00</span><span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token number">3</span>h<span class="token punctuation">,</span> <span class="token number">1</span>d<span class="token punctuation">)</span><span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>which means:</p><p>Since the user specifies the sliding step parameter as 1d, the <code>GROUP BY</code> statement will move the time interval <code>1 day</code> long instead of <code>3 hours</code> as default.</p><p>That means we want to fetch all the data of 00:00:00 to 02:59:59 every day from 2017-11-01 to 2017-11-07.</p><p>The first parameter of the <code>GROUP BY</code> statement above is the display window parameter, which determines the final display range is [2017-11-01T00:00:00, 2017-11-07T23:00:00).</p><p>The second parameter of the <code>GROUP BY</code> statement above is the time interval for dividing the time axis. Taking this parameter (3h) as time interval and the startTime of the display window as the dividing origin, the time axis is divided into several continuous intervals, which are [2017-11-01T00:00:00, 2017-11-01T03:00:00), [2017-11-02T00:00:00, 2017-11-02T03:00:00), [2017-11-03T00:00:00, 2017-11-03T03:00:00), etc.</p><p>The third parameter of the <code>GROUP BY</code> statement above is the sliding step for each time interval moving.</p><p>Then the system will use the time and value filtering condition in the <code>WHERE</code> clause and the first parameter of the <code>GROUP BY</code> statement as the data filtering condition to obtain the data satisfying the filtering condition (which in this case is the data in the range of [2017-11-01T00:00:00, 2017-11-07T23:00:00]), and map these data to the previously segmented time axis (in this case there are mapped data in every 3-hour period for each day from 2017-11-01T00:00:00 to 2017-11-07T23:00:00:00).</p><p>Since there is data for each time period in the result range to be displayed, the execution result of the SQL statement is shown below:</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>+-----------------------------+-------------------------------+----------------------------------------+
|                         Time|count(root.ln.wf01.wt01.status)|max_value(root.ln.wf01.wt01.temperature)|
+-----------------------------+-------------------------------+----------------------------------------+
|2017-11-01T00:00:00.000+08:00|                            180|                                   25.98|
|2017-11-02T00:00:00.000+08:00|                            180|                                   25.98|
|2017-11-03T00:00:00.000+08:00|                            180|                                   25.96|
|2017-11-04T00:00:00.000+08:00|                            180|                                   25.96|
|2017-11-05T00:00:00.000+08:00|                            180|                                    26.0|
|2017-11-06T00:00:00.000+08:00|                            180|                                   25.85|
|2017-11-07T00:00:00.000+08:00|                            180|                                   25.99|
+-----------------------------+-------------------------------+----------------------------------------+
Total line number = 7
It costs 0.006s
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>The sliding step can be smaller than the interval, in which case there is overlapping time between the aggregation windows (similar to a sliding window).</p><p>The SQL statement is:</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> <span class="token function">count</span><span class="token punctuation">(</span><span class="token keyword">status</span><span class="token punctuation">)</span><span class="token punctuation">,</span> max_value<span class="token punctuation">(</span>temperature<span class="token punctuation">)</span> <span class="token keyword">from</span> root<span class="token punctuation">.</span>ln<span class="token punctuation">.</span>wf01<span class="token punctuation">.</span>wt01 <span class="token keyword">group</span> <span class="token keyword">by</span> <span class="token punctuation">(</span><span class="token punctuation">[</span><span class="token number">2017</span><span class="token operator">-</span><span class="token number">11</span><span class="token operator">-</span><span class="token number">01</span> <span class="token number">00</span>:<span class="token number">00</span>:<span class="token number">00</span><span class="token punctuation">,</span> <span class="token number">2017</span><span class="token operator">-</span><span class="token number">11</span><span class="token operator">-</span><span class="token number">01</span> <span class="token number">10</span>:<span class="token number">00</span>:<span class="token number">00</span><span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token number">4</span>h<span class="token punctuation">,</span> <span class="token number">2</span>h<span class="token punctuation">)</span><span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>The execution result of the SQL statement is shown below:</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>+-----------------------------+-------------------------------+----------------------------------------+
|                         Time|count(root.ln.wf01.wt01.status)|max_value(root.ln.wf01.wt01.temperature)|
+-----------------------------+-------------------------------+----------------------------------------+
|2017-11-01T00:00:00.000+08:00|                            180|                                   25.98|
|2017-11-01T02:00:00.000+08:00|                            180|                                   25.98|
|2017-11-01T04:00:00.000+08:00|                            180|                                   25.96|
|2017-11-01T06:00:00.000+08:00|                            180|                                   25.96|
|2017-11-01T08:00:00.000+08:00|                            180|                                    26.0|
+-----------------------------+-------------------------------+----------------------------------------+
Total line number = 5
It costs 0.006s
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><h5 id="aggregate-by-natural-month" tabindex="-1"><a class="header-anchor" href="#aggregate-by-natural-month"><span>Aggregate by Natural Month</span></a></h5><p>The SQL statement is:</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> <span class="token function">count</span><span class="token punctuation">(</span><span class="token keyword">status</span><span class="token punctuation">)</span> <span class="token keyword">from</span> root<span class="token punctuation">.</span>ln<span class="token punctuation">.</span>wf01<span class="token punctuation">.</span>wt01 <span class="token keyword">group</span> <span class="token keyword">by</span><span class="token punctuation">(</span><span class="token punctuation">[</span><span class="token number">2017</span><span class="token operator">-</span><span class="token number">11</span><span class="token operator">-</span><span class="token number">01</span>T00:<span class="token number">00</span>:<span class="token number">00</span><span class="token punctuation">,</span> <span class="token number">2019</span><span class="token operator">-</span><span class="token number">11</span><span class="token operator">-</span><span class="token number">07</span>T23:<span class="token number">00</span>:<span class="token number">00</span><span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token number">1</span>mo<span class="token punctuation">,</span> <span class="token number">2</span>mo<span class="token punctuation">)</span><span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>which means:</p><p>Since the user specifies the sliding step parameter as <code>2mo</code>, the <code>GROUP BY</code> statement will move the time interval <code>2 months</code> long instead of <code>1 month</code> as default.</p><p>The first parameter of the <code>GROUP BY</code> statement above is the display window parameter, which determines the final display range is [2017-11-01T00:00:00, 2019-11-07T23:00:00).</p><p>The start time is 2017-11-01T00:00:00. The sliding step will increment monthly based on the start date, and the 1st day of the month will be used as the time interval&#39;s start time.</p><p>The second parameter of the <code>GROUP BY</code> statement above is the time interval for dividing the time axis. Taking this parameter (1mo) as time interval and the startTime of the display window as the dividing origin, the time axis is divided into several continuous intervals, which are [2017-11-01T00:00:00, 2017-12-01T00:00:00), [2018-02-01T00:00:00, 2018-03-01T00:00:00), [2018-05-03T00:00:00, 2018-06-01T00:00:00)), etc.</p><p>The third parameter of the <code>GROUP BY</code> statement above is the sliding step for each time interval moving.</p><p>Then the system will use the time and value filtering condition in the <code>WHERE</code> clause and the first parameter of the <code>GROUP BY</code> statement as the data filtering condition to obtain the data satisfying the filtering condition (which in this case is the data in the range of (2017-11-01T00:00:00, 2019-11-07T23:00:00], and map these data to the previously segmented time axis (in this case there are mapped data of the first month in every two month period from 2017-11-01T00:00:00 to 2019-11-07T23:00:00).</p><p>The SQL execution result is:</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>+-----------------------------+-------------------------------+
|                         Time|count(root.ln.wf01.wt01.status)|
+-----------------------------+-------------------------------+
|2017-11-01T00:00:00.000+08:00|                            259|
|2018-01-01T00:00:00.000+08:00|                            250|
|2018-03-01T00:00:00.000+08:00|                            259|
|2018-05-01T00:00:00.000+08:00|                            251|
|2018-07-01T00:00:00.000+08:00|                            242|
|2018-09-01T00:00:00.000+08:00|                            225|
|2018-11-01T00:00:00.000+08:00|                            216|
|2019-01-01T00:00:00.000+08:00|                            207|
|2019-03-01T00:00:00.000+08:00|                            216|
|2019-05-01T00:00:00.000+08:00|                            207|
|2019-07-01T00:00:00.000+08:00|                            199|
|2019-09-01T00:00:00.000+08:00|                            181|
|2019-11-01T00:00:00.000+08:00|                             60|
+-----------------------------+-------------------------------+
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>The SQL statement is:</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> <span class="token function">count</span><span class="token punctuation">(</span><span class="token keyword">status</span><span class="token punctuation">)</span> <span class="token keyword">from</span> root<span class="token punctuation">.</span>ln<span class="token punctuation">.</span>wf01<span class="token punctuation">.</span>wt01 <span class="token keyword">group</span> <span class="token keyword">by</span><span class="token punctuation">(</span><span class="token punctuation">[</span><span class="token number">2017</span><span class="token operator">-</span><span class="token number">10</span><span class="token operator">-</span><span class="token number">31</span>T00:<span class="token number">00</span>:<span class="token number">00</span><span class="token punctuation">,</span> <span class="token number">2019</span><span class="token operator">-</span><span class="token number">11</span><span class="token operator">-</span><span class="token number">07</span>T23:<span class="token number">00</span>:<span class="token number">00</span><span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token number">1</span>mo<span class="token punctuation">,</span> <span class="token number">2</span>mo<span class="token punctuation">)</span><span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>which means:</p><p>Since the user specifies the sliding step parameter as <code>2mo</code>, the <code>GROUP BY</code> statement will move the time interval <code>2 months</code> long instead of <code>1 month</code> as default.</p><p>The first parameter of the <code>GROUP BY</code> statement above is the display window parameter, which determines the final display range is [2017-10-31T00:00:00, 2019-11-07T23:00:00).</p><p>Different from the previous example, the start time is set to 2017-10-31T00:00:00. The sliding step will increment monthly based on the start date, and the 31st day of the month meaning the last day of the month will be used as the time interval&#39;s start time. If the start time is set to the 30th date, the sliding step will use the 30th or the last day of the month.</p><p>The start time is 2017-10-31T00:00:00. The sliding step will increment monthly based on the start time, and the 1st day of the month will be used as the time interval&#39;s start time.</p><p>The second parameter of the <code>GROUP BY</code> statement above is the time interval for dividing the time axis. Taking this parameter (1mo) as time interval and the startTime of the display window as the dividing origin, the time axis is divided into several continuous intervals, which are [2017-10-31T00:00:00, 2017-11-31T00:00:00), [2018-02-31T00:00:00, 2018-03-31T00:00:00), [2018-05-31T00:00:00, 2018-06-31T00:00:00), etc.</p><p>The third parameter of the <code>GROUP BY</code> statement above is the sliding step for each time interval moving.</p><p>Then the system will use the time and value filtering condition in the <code>WHERE</code> clause and the first parameter of the <code>GROUP BY</code> statement as the data filtering condition to obtain the data satisfying the filtering condition (which in this case is the data in the range of [2017-10-31T00:00:00, 2019-11-07T23:00:00) and map these data to the previously segmented time axis (in this case there are mapped data of the first month in every two month period from 2017-10-31T00:00:00 to 2019-11-07T23:00:00).</p><p>The SQL execution result is:</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>+-----------------------------+-------------------------------+
|                         Time|count(root.ln.wf01.wt01.status)|
+-----------------------------+-------------------------------+
|2017-10-31T00:00:00.000+08:00|                            251|
|2017-12-31T00:00:00.000+08:00|                            250|
|2018-02-28T00:00:00.000+08:00|                            259|
|2018-04-30T00:00:00.000+08:00|                            250|
|2018-06-30T00:00:00.000+08:00|                            242|
|2018-08-31T00:00:00.000+08:00|                            225|
|2018-10-31T00:00:00.000+08:00|                            216|
|2018-12-31T00:00:00.000+08:00|                            208|
|2019-02-28T00:00:00.000+08:00|                            216|
|2019-04-30T00:00:00.000+08:00|                            208|
|2019-06-30T00:00:00.000+08:00|                            199|
|2019-08-31T00:00:00.000+08:00|                            181|
|2019-10-31T00:00:00.000+08:00|                             69|
+-----------------------------+-------------------------------+
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><h5 id="left-open-and-right-close-range" tabindex="-1"><a class="header-anchor" href="#left-open-and-right-close-range"><span>Left Open And Right Close Range</span></a></h5><p>The SQL statement is:</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> <span class="token function">count</span><span class="token punctuation">(</span><span class="token keyword">status</span><span class="token punctuation">)</span> <span class="token keyword">from</span> root<span class="token punctuation">.</span>ln<span class="token punctuation">.</span>wf01<span class="token punctuation">.</span>wt01 <span class="token keyword">group</span> <span class="token keyword">by</span> <span class="token punctuation">(</span><span class="token punctuation">(</span><span class="token number">2017</span><span class="token operator">-</span><span class="token number">11</span><span class="token operator">-</span><span class="token number">01</span>T00:<span class="token number">00</span>:<span class="token number">00</span><span class="token punctuation">,</span> <span class="token number">2017</span><span class="token operator">-</span><span class="token number">11</span><span class="token operator">-</span><span class="token number">07</span>T23:<span class="token number">00</span>:<span class="token number">00</span><span class="token punctuation">]</span><span class="token punctuation">,</span><span class="token number">1</span>d<span class="token punctuation">)</span><span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>In this sql, the time interval is left open and right close, so we won&#39;t include the value of timestamp 2017-11-01T00:00:00 and instead we will include the value of timestamp 2017-11-07T23:00:00.</p><p>We will get the result like following:</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>+-----------------------------+-------------------------------+
|                         Time|count(root.ln.wf01.wt01.status)|
+-----------------------------+-------------------------------+
|2017-11-02T00:00:00.000+08:00|                           1440|
|2017-11-03T00:00:00.000+08:00|                           1440|
|2017-11-04T00:00:00.000+08:00|                           1440|
|2017-11-05T00:00:00.000+08:00|                           1440|
|2017-11-06T00:00:00.000+08:00|                           1440|
|2017-11-07T00:00:00.000+08:00|                           1440|
|2017-11-07T23:00:00.000+08:00|                           1380|
+-----------------------------+-------------------------------+
Total line number = 7
It costs 0.004s
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><h4 id="aggregation-by-variation" tabindex="-1"><a class="header-anchor" href="#aggregation-by-variation"><span>Aggregation By Variation</span></a></h4><p>IoTDB supports grouping by continuous stable values through the <code>GROUP BY VARIATION</code> statement.</p><p>Group-By-Variation wil set the first point in group as the base point,<br> then if the difference between the new data and base point is small than or equal to delta,<br> the data point will be grouped together and execute aggregation query (The calculation of difference and the meaning of delte are introduced below). The groups won&#39;t overlap and there is no fixed start time and end time.<br> The syntax of clause is as follows:</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">group</span> <span class="token keyword">by</span> variation<span class="token punctuation">(</span>controlExpression<span class="token punctuation">[</span><span class="token punctuation">,</span>delta<span class="token punctuation">]</span><span class="token punctuation">[</span><span class="token punctuation">,</span>ignoreNull<span class="token operator">=</span><span class="token boolean">true</span><span class="token operator">/</span><span class="token boolean">false</span><span class="token punctuation">]</span><span class="token punctuation">)</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>The different parameters mean:</p><ul><li>controlExpression</li></ul><p>The value that is used to calculate difference. It can be any columns or the expression of them.</p><ul><li>delta</li></ul><p>The threshold that is used when grouping. The difference of controlExpression between the first data point and new data point should less than or equal to delta.<br> When delta is zero, all the continuous data with equal expression value will be grouped into the same group.</p><ul><li>ignoreNull</li></ul><p>Used to specify how to deal with the data when the value of controlExpression is null. When ignoreNull is false, null will be treated as a new value and when ignoreNull is true, the data point will be directly skipped.</p><p>The supported return types of controlExpression and how to deal with null value when ignoreNull is false are shown in the following table:</p><table><thead><tr><th>delta</th><th>Return Type Supported By controlExpression</th><th>The Handling of null when ignoreNull is False</th></tr></thead><tbody><tr><td>delta!=0</td><td>INT32、INT64、FLOAT、DOUBLE</td><td>If the processing group doesn&#39;t contains null, null value should be treated as infinity/infinitesimal and will end current group.<br>Continuous null values are treated as stable values and assigned to the same group.</td></tr><tr><td>delta=0</td><td>TEXT、BINARY、INT32、INT64、FLOAT、DOUBLE</td><td>Null is treated as a new value in a new group and continuous nulls belong to the same group.</td></tr></tbody></table><img style="width:100%;max-width:800px;max-height:600px;margin-left:auto;margin-right:auto;display:block;" src="https://alioss.timecho.com/docs/img/UserGuide/Process-Data/GroupBy/groupByVariation.jpeg" alt="groupByVariation"><h5 id="precautions-for-use" tabindex="-1"><a class="header-anchor" href="#precautions-for-use"><span>Precautions for Use</span></a></h5><ol><li>The result of controlExpression should be a unique value. If multiple columns appear after using wildcard stitching, an error will be reported.</li><li>For a group in resultSet, the time column output the start time of the group by default. __endTime can be used in select clause to output the endTime of groups in resultSet.</li><li>Each device is grouped separately when used with <code>ALIGN BY DEVICE</code>.</li><li>Delta is zero and ignoreNull is true by default.</li><li>Currently <code>GROUP BY VARIATION</code> is not supported with <code>GROUP BY LEVEL</code>.</li></ol><p>Using the raw data below, several examples of <code>GROUP BY VARIAITON</code> queries will be given.</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>+-----------------------------+-------+-------+-------+--------+-------+-------+
|                         Time|     s1|     s2|     s3|      s4|     s5|     s6|
+-----------------------------+-------+-------+-------+--------+-------+-------+
|1970-01-01T08:00:00.000+08:00|    4.5|    9.0|    0.0|    45.0|    9.0|   8.25|
|1970-01-01T08:00:00.010+08:00|   null|   19.0|   10.0|   145.0|   19.0|   8.25|
|1970-01-01T08:00:00.020+08:00|   24.5|   29.0|   null|   245.0|   29.0|   null|
|1970-01-01T08:00:00.030+08:00|   34.5|   null|   30.0|   345.0|   null|   null|
|1970-01-01T08:00:00.040+08:00|   44.5|   49.0|   40.0|   445.0|   49.0|   8.25|
|1970-01-01T08:00:00.050+08:00|   null|   59.0|   50.0|   545.0|   59.0|   6.25|
|1970-01-01T08:00:00.060+08:00|   64.5|   69.0|   60.0|   645.0|   69.0|   null|
|1970-01-01T08:00:00.070+08:00|   74.5|   79.0|   null|    null|   79.0|   3.25|
|1970-01-01T08:00:00.080+08:00|   84.5|   89.0|   80.0|   845.0|   89.0|   3.25|
|1970-01-01T08:00:00.090+08:00|   94.5|   99.0|   90.0|   945.0|   99.0|   3.25|
|1970-01-01T08:00:00.150+08:00|   66.5|   77.0|   90.0|   945.0|   99.0|   9.25|
+-----------------------------+-------+-------+-------+--------+-------+-------+
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><h5 id="delta-0" tabindex="-1"><a class="header-anchor" href="#delta-0"><span>delta = 0</span></a></h5><p>The sql is shown below:</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> __endTime<span class="token punctuation">,</span> <span class="token function">avg</span><span class="token punctuation">(</span>s1<span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token function">count</span><span class="token punctuation">(</span>s2<span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token function">sum</span><span class="token punctuation">(</span>s3<span class="token punctuation">)</span> <span class="token keyword">from</span> root<span class="token punctuation">.</span>sg<span class="token punctuation">.</span>d <span class="token keyword">group</span> <span class="token keyword">by</span> variation<span class="token punctuation">(</span>s6<span class="token punctuation">)</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>Get the result below which ignores the row with null value in <code>s6</code>.</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>+-----------------------------+-----------------------------+-----------------+-------------------+-----------------+
|                         Time|                    __endTime|avg(root.sg.d.s1)|count(root.sg.d.s2)|sum(root.sg.d.s3)|
+-----------------------------+-----------------------------+-----------------+-------------------+-----------------+
|1970-01-01T08:00:00.000+08:00|1970-01-01T08:00:00.040+08:00|             24.5|                  3|             50.0|
|1970-01-01T08:00:00.050+08:00|1970-01-01T08:00:00.050+08:00|             null|                  1|             50.0|
|1970-01-01T08:00:00.070+08:00|1970-01-01T08:00:00.090+08:00|             84.5|                  3|            170.0|
|1970-01-01T08:00:00.150+08:00|1970-01-01T08:00:00.150+08:00|             66.5|                  1|             90.0|
+-----------------------------+-----------------------------+-----------------+-------------------+-----------------+
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>when ignoreNull is false, the row with null value in <code>s6</code> will be considered.</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> __endTime<span class="token punctuation">,</span> <span class="token function">avg</span><span class="token punctuation">(</span>s1<span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token function">count</span><span class="token punctuation">(</span>s2<span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token function">sum</span><span class="token punctuation">(</span>s3<span class="token punctuation">)</span> <span class="token keyword">from</span> root<span class="token punctuation">.</span>sg<span class="token punctuation">.</span>d <span class="token keyword">group</span> <span class="token keyword">by</span> variation<span class="token punctuation">(</span>s6<span class="token punctuation">,</span> ignoreNull<span class="token operator">=</span><span class="token boolean">false</span><span class="token punctuation">)</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>Get the following result.</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>+-----------------------------+-----------------------------+-----------------+-------------------+-----------------+
|                         Time|                    __endTime|avg(root.sg.d.s1)|count(root.sg.d.s2)|sum(root.sg.d.s3)|
+-----------------------------+-----------------------------+-----------------+-------------------+-----------------+
|1970-01-01T08:00:00.000+08:00|1970-01-01T08:00:00.010+08:00|              4.5|                  2|             10.0|
|1970-01-01T08:00:00.020+08:00|1970-01-01T08:00:00.030+08:00|             29.5|                  1|             30.0|
|1970-01-01T08:00:00.040+08:00|1970-01-01T08:00:00.040+08:00|             44.5|                  1|             40.0|
|1970-01-01T08:00:00.050+08:00|1970-01-01T08:00:00.050+08:00|             null|                  1|             50.0|
|1970-01-01T08:00:00.060+08:00|1970-01-01T08:00:00.060+08:00|             64.5|                  1|             60.0|
|1970-01-01T08:00:00.070+08:00|1970-01-01T08:00:00.090+08:00|             84.5|                  3|            170.0|
|1970-01-01T08:00:00.150+08:00|1970-01-01T08:00:00.150+08:00|             66.5|                  1|             90.0|
+-----------------------------+-----------------------------+-----------------+-------------------+-----------------+
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><h5 id="delta-0-1" tabindex="-1"><a class="header-anchor" href="#delta-0-1"><span>delta !=0</span></a></h5><p>The sql is shown below:</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> __endTime<span class="token punctuation">,</span> <span class="token function">avg</span><span class="token punctuation">(</span>s1<span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token function">count</span><span class="token punctuation">(</span>s2<span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token function">sum</span><span class="token punctuation">(</span>s3<span class="token punctuation">)</span> <span class="token keyword">from</span> root<span class="token punctuation">.</span>sg<span class="token punctuation">.</span>d <span class="token keyword">group</span> <span class="token keyword">by</span> variation<span class="token punctuation">(</span>s6<span class="token punctuation">,</span> <span class="token number">4</span><span class="token punctuation">)</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>Get the result below:</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>+-----------------------------+-----------------------------+-----------------+-------------------+-----------------+
|                         Time|                    __endTime|avg(root.sg.d.s1)|count(root.sg.d.s2)|sum(root.sg.d.s3)|
+-----------------------------+-----------------------------+-----------------+-------------------+-----------------+
|1970-01-01T08:00:00.000+08:00|1970-01-01T08:00:00.050+08:00|             24.5|                  4|            100.0|
|1970-01-01T08:00:00.070+08:00|1970-01-01T08:00:00.090+08:00|             84.5|                  3|            170.0|
|1970-01-01T08:00:00.150+08:00|1970-01-01T08:00:00.150+08:00|             66.5|                  1|             90.0|
+-----------------------------+-----------------------------+-----------------+-------------------+-----------------+
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>The sql is shown below:</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> __endTime<span class="token punctuation">,</span> <span class="token function">avg</span><span class="token punctuation">(</span>s1<span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token function">count</span><span class="token punctuation">(</span>s2<span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token function">sum</span><span class="token punctuation">(</span>s3<span class="token punctuation">)</span> <span class="token keyword">from</span> root<span class="token punctuation">.</span>sg<span class="token punctuation">.</span>d <span class="token keyword">group</span> <span class="token keyword">by</span> variation<span class="token punctuation">(</span>s6<span class="token operator">+</span>s5<span class="token punctuation">,</span> <span class="token number">10</span><span class="token punctuation">)</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>Get the result below:</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>+-----------------------------+-----------------------------+-----------------+-------------------+-----------------+
|                         Time|                    __endTime|avg(root.sg.d.s1)|count(root.sg.d.s2)|sum(root.sg.d.s3)|
+-----------------------------+-----------------------------+-----------------+-------------------+-----------------+
|1970-01-01T08:00:00.000+08:00|1970-01-01T08:00:00.010+08:00|              4.5|                  2|             10.0|
|1970-01-01T08:00:00.040+08:00|1970-01-01T08:00:00.050+08:00|             44.5|                  2|             90.0|
|1970-01-01T08:00:00.070+08:00|1970-01-01T08:00:00.080+08:00|             79.5|                  2|             80.0|
|1970-01-01T08:00:00.090+08:00|1970-01-01T08:00:00.150+08:00|             80.5|                  2|            180.0|
+-----------------------------+-----------------------------+-----------------+-------------------+-----------------+
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><h4 id="aggregation-by-condition" tabindex="-1"><a class="header-anchor" href="#aggregation-by-condition"><span>Aggregation By Condition</span></a></h4><p>When you need to filter the data according to a specific condition and group the continuous ones for an aggregation query.<br><code>GROUP BY CONDITION</code> is suitable for you.The rows which don&#39;t meet the given condition will be simply ignored because they don&#39;t belong to any group.<br> Its syntax is defined below:</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">group</span> <span class="token keyword">by</span> condition<span class="token punctuation">(</span>predict<span class="token punctuation">,</span><span class="token punctuation">[</span>keep<span class="token operator">&gt;</span><span class="token operator">/</span><span class="token operator">&gt;=</span><span class="token operator">/</span><span class="token operator">=</span><span class="token operator">/</span><span class="token operator">&lt;=</span><span class="token operator">/</span><span class="token operator">&lt;</span><span class="token punctuation">]</span>threshold<span class="token punctuation">,</span><span class="token punctuation">[</span><span class="token punctuation">,</span>ignoreNull<span class="token operator">=</span><span class="token boolean">true</span><span class="token operator">/</span><span class="token boolean">false</span><span class="token punctuation">]</span><span class="token punctuation">)</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><ul><li>predict</li></ul><p>Any legal expression return the type of boolean for filtering in grouping.</p><ul><li>[keep&gt;/&gt;=/=/&lt;=/&lt;]threshold</li></ul><p>Keep expression is used to specify the number of continuous rows that meet the <code>predict</code> condition to form a group. Only the number of rows in group satisfy the keep condition, the result of group will be output.<br> Keep expression consists of a &#39;keep&#39; string and a threshold of type <code>long</code> or a single &#39;long&#39; type data.</p><ul><li>ignoreNull=true/false</li></ul><p>Used to specify how to handle data rows that encounter null predict, skip the row when it&#39;s true and end current group when it&#39;s false.</p><h5 id="precautions-for-use-1" tabindex="-1"><a class="header-anchor" href="#precautions-for-use-1"><span>Precautions for Use</span></a></h5><ol><li>keep condition is required in the query, but you can omit the &#39;keep&#39; string and given a <code>long</code> number which defaults to &#39;keep=long number&#39; condition.</li><li>IgnoreNull defaults to true.</li><li>For a group in resultSet, the time column output the start time of the group by default. __endTime can be used in select clause to output the endTime of groups in resultSet.</li><li>Each device is grouped separately when used with <code>ALIGN BY DEVICE</code>.</li><li>Currently <code>GROUP BY CONDITION</code> is not supported with <code>GROUP BY LEVEL</code>.</li></ol><p>For the following raw data, several query examples are given below:</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>+-----------------------------+-------------------------+-------------------------------------+------------------------------------+
|                         Time|root.sg.beijing.car01.soc|root.sg.beijing.car01.charging_status|root.sg.beijing.car01.vehicle_status|
+-----------------------------+-------------------------+-------------------------------------+------------------------------------+
|1970-01-01T08:00:00.001+08:00|                     14.0|                                    1|                                   1|
|1970-01-01T08:00:00.002+08:00|                     16.0|                                    1|                                   1|
|1970-01-01T08:00:00.003+08:00|                     16.0|                                    0|                                   1|
|1970-01-01T08:00:00.004+08:00|                     16.0|                                    0|                                   1|
|1970-01-01T08:00:00.005+08:00|                     18.0|                                    1|                                   1|
|1970-01-01T08:00:00.006+08:00|                     24.0|                                    1|                                   1|
|1970-01-01T08:00:00.007+08:00|                     36.0|                                    1|                                   1|
|1970-01-01T08:00:00.008+08:00|                     36.0|                                 null|                                   1|
|1970-01-01T08:00:00.009+08:00|                     45.0|                                    1|                                   1|
|1970-01-01T08:00:00.010+08:00|                     60.0|                                    1|                                   1|
+-----------------------------+-------------------------+-------------------------------------+------------------------------------+
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>The sql statement to query data with at least two continuous row shown below:</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> max_time<span class="token punctuation">(</span>charging_status<span class="token punctuation">)</span><span class="token punctuation">,</span><span class="token function">count</span><span class="token punctuation">(</span>vehicle_status<span class="token punctuation">)</span><span class="token punctuation">,</span>last_value<span class="token punctuation">(</span>soc<span class="token punctuation">)</span> <span class="token keyword">from</span> root<span class="token punctuation">.</span><span class="token operator">*</span><span class="token operator">*</span> <span class="token keyword">group</span> <span class="token keyword">by</span> condition<span class="token punctuation">(</span>charging_status<span class="token operator">=</span><span class="token number">1</span><span class="token punctuation">,</span>KEEP<span class="token operator">&gt;=</span><span class="token number">2</span><span class="token punctuation">,</span>ignoringNull<span class="token operator">=</span><span class="token boolean">true</span><span class="token punctuation">)</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>Get the result below:</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>+-----------------------------+-----------------------------------------------+-------------------------------------------+-------------------------------------+
|                         Time|max_time(root.sg.beijing.car01.charging_status)|count(root.sg.beijing.car01.vehicle_status)|last_value(root.sg.beijing.car01.soc)|
+-----------------------------+-----------------------------------------------+-------------------------------------------+-------------------------------------+
|1970-01-01T08:00:00.001+08:00|                                              2|                                          2|                                 16.0|
|1970-01-01T08:00:00.005+08:00|                                             10|                                          5|                                 60.0|
+-----------------------------+-----------------------------------------------+-------------------------------------------+-------------------------------------+
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>When ignoreNull is false, the null value will be treated as a row that doesn&#39;t meet the condition.</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> max_time<span class="token punctuation">(</span>charging_status<span class="token punctuation">)</span><span class="token punctuation">,</span><span class="token function">count</span><span class="token punctuation">(</span>vehicle_status<span class="token punctuation">)</span><span class="token punctuation">,</span>last_value<span class="token punctuation">(</span>soc<span class="token punctuation">)</span> <span class="token keyword">from</span> root<span class="token punctuation">.</span><span class="token operator">*</span><span class="token operator">*</span> <span class="token keyword">group</span> <span class="token keyword">by</span> condition<span class="token punctuation">(</span>charging_status<span class="token operator">=</span><span class="token number">1</span><span class="token punctuation">,</span>KEEP<span class="token operator">&gt;=</span><span class="token number">2</span><span class="token punctuation">,</span>ignoringNull<span class="token operator">=</span><span class="token boolean">false</span><span class="token punctuation">)</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>Get the result below, the original group is split.</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>+-----------------------------+-----------------------------------------------+-------------------------------------------+-------------------------------------+
|                         Time|max_time(root.sg.beijing.car01.charging_status)|count(root.sg.beijing.car01.vehicle_status)|last_value(root.sg.beijing.car01.soc)|
+-----------------------------+-----------------------------------------------+-------------------------------------------+-------------------------------------+
|1970-01-01T08:00:00.001+08:00|                                              2|                                          2|                                 16.0|
|1970-01-01T08:00:00.005+08:00|                                              7|                                          3|                                 36.0|
|1970-01-01T08:00:00.009+08:00|                                             10|                                          2|                                 60.0|
+-----------------------------+-----------------------------------------------+-------------------------------------------+-------------------------------------+
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><h4 id="aggregation-by-session" tabindex="-1"><a class="header-anchor" href="#aggregation-by-session"><span>Aggregation By Session</span></a></h4><p><code>GROUP BY SESSION</code> can be used to group data according to the interval of the time. Data with a time interval less than or equal to the given threshold will be assigned to the same group.<br> For example, in industrial scenarios, devices don&#39;t always run continuously, <code>GROUP BY SESSION</code> will group the data generated by each access session of the device.<br> Its syntax is defined as follows:</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">group</span> <span class="token keyword">by</span> <span class="token keyword">session</span><span class="token punctuation">(</span>timeInterval<span class="token punctuation">)</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><ul><li>timeInterval</li></ul><p>A given interval threshold to create a new group of data when the difference between the time of data is greater than the threshold.</p><p>The figure below is a grouping diagram under <code>GROUP BY SESSION</code>.</p><img style="width:100%;max-width:800px;max-height:600px;margin-left:auto;margin-right:auto;display:block;" src="https://alioss.timecho.com/docs/img/UserGuide/Process-Data/GroupBy/groupBySession.jpeg" alt="groupBySession"><h5 id="precautions-for-use-2" tabindex="-1"><a class="header-anchor" href="#precautions-for-use-2"><span>Precautions for Use</span></a></h5><ol><li>For a group in resultSet, the time column output the start time of the group by default. __endTime can be used in select clause to output the endTime of groups in resultSet.</li><li>Each device is grouped separately when used with <code>ALIGN BY DEVICE</code>.</li><li>Currently <code>GROUP BY SESSION</code> is not supported with <code>GROUP BY LEVEL</code>.</li></ol><p>For the raw data below, a few query examples are given:</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>+-----------------------------+-----------------+-----------+--------+------+
|                         Time|           Device|temperature|hardware|status|
+-----------------------------+-----------------+-----------+--------+------+
|1970-01-01T08:00:01.000+08:00|root.ln.wf02.wt01|       35.7|      11| false|
|1970-01-01T08:00:02.000+08:00|root.ln.wf02.wt01|       35.8|      22|  true|
|1970-01-01T08:00:03.000+08:00|root.ln.wf02.wt01|       35.4|      33| false|
|1970-01-01T08:00:04.000+08:00|root.ln.wf02.wt01|       36.4|      44| false|
|1970-01-01T08:00:05.000+08:00|root.ln.wf02.wt01|       36.8|      55| false|
|1970-01-01T08:00:10.000+08:00|root.ln.wf02.wt01|       36.8|     110| false|
|1970-01-01T08:00:20.000+08:00|root.ln.wf02.wt01|       37.8|     220|  true|
|1970-01-01T08:00:30.000+08:00|root.ln.wf02.wt01|       37.5|     330| false|
|1970-01-01T08:00:40.000+08:00|root.ln.wf02.wt01|       37.4|     440| false|
|1970-01-01T08:00:50.000+08:00|root.ln.wf02.wt01|       37.9|     550| false|
|1970-01-01T08:01:40.000+08:00|root.ln.wf02.wt01|       38.0|     110| false|
|1970-01-01T08:02:30.000+08:00|root.ln.wf02.wt01|       38.8|     220|  true|
|1970-01-01T08:03:20.000+08:00|root.ln.wf02.wt01|       38.6|     330| false|
|1970-01-01T08:04:20.000+08:00|root.ln.wf02.wt01|       38.4|     440| false|
|1970-01-01T08:05:20.000+08:00|root.ln.wf02.wt01|       38.3|     550| false|
|1970-01-01T08:06:40.000+08:00|root.ln.wf02.wt01|       null|       0|  null|
|1970-01-01T08:07:50.000+08:00|root.ln.wf02.wt01|       null|       0|  null|
|1970-01-01T08:08:00.000+08:00|root.ln.wf02.wt01|       null|       0|  null|
|1970-01-02T08:08:01.000+08:00|root.ln.wf02.wt01|       38.2|     110| false|
|1970-01-02T08:08:02.000+08:00|root.ln.wf02.wt01|       37.5|     220|  true|
|1970-01-02T08:08:03.000+08:00|root.ln.wf02.wt01|       37.4|     330| false|
|1970-01-02T08:08:04.000+08:00|root.ln.wf02.wt01|       36.8|     440| false|
|1970-01-02T08:08:05.000+08:00|root.ln.wf02.wt01|       37.4|     550| false|
+-----------------------------+-----------------+-----------+--------+------+
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>TimeInterval can be set by different time units, the sql is shown below:</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> __endTime<span class="token punctuation">,</span><span class="token function">count</span><span class="token punctuation">(</span><span class="token operator">*</span><span class="token punctuation">)</span> <span class="token keyword">from</span> root<span class="token punctuation">.</span><span class="token operator">*</span><span class="token operator">*</span> <span class="token keyword">group</span> <span class="token keyword">by</span> <span class="token keyword">session</span><span class="token punctuation">(</span><span class="token number">1</span>d<span class="token punctuation">)</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>Get the result：</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>+-----------------------------+-----------------------------+------------------------------------+---------------------------------+-------------------------------+
|                         Time|                    __endTime|count(root.ln.wf02.wt01.temperature)|count(root.ln.wf02.wt01.hardware)|count(root.ln.wf02.wt01.status)|
+-----------------------------+-----------------------------+------------------------------------+---------------------------------+-------------------------------+
|1970-01-01T08:00:01.000+08:00|1970-01-01T08:08:00.000+08:00|                                  15|                               18|                             15|
|1970-01-02T08:08:01.000+08:00|1970-01-02T08:08:05.000+08:00|                                   5|                                5|                              5|
+-----------------------------+-----------------------------+------------------------------------+---------------------------------+-------------------------------+
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>It can be also used with <code>HAVING</code> and <code>ALIGN BY DEVICE</code> clauses.</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> __endTime<span class="token punctuation">,</span><span class="token function">sum</span><span class="token punctuation">(</span>hardware<span class="token punctuation">)</span> <span class="token keyword">from</span> root<span class="token punctuation">.</span>ln<span class="token punctuation">.</span>wf02<span class="token punctuation">.</span>wt01 <span class="token keyword">group</span> <span class="token keyword">by</span> <span class="token keyword">session</span><span class="token punctuation">(</span><span class="token number">50</span>s<span class="token punctuation">)</span> <span class="token keyword">having</span> <span class="token function">sum</span><span class="token punctuation">(</span>hardware<span class="token punctuation">)</span><span class="token operator">&gt;</span><span class="token number">0</span> align <span class="token keyword">by</span> device
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>Get the result below:</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>+-----------------------------+-----------------+-----------------------------+-------------+
|                         Time|           Device|                    __endTime|sum(hardware)|
+-----------------------------+-----------------+-----------------------------+-------------+
|1970-01-01T08:00:01.000+08:00|root.ln.wf02.wt01|1970-01-01T08:03:20.000+08:00|       2475.0|
|1970-01-01T08:04:20.000+08:00|root.ln.wf02.wt01|1970-01-01T08:04:20.000+08:00|        440.0|
|1970-01-01T08:05:20.000+08:00|root.ln.wf02.wt01|1970-01-01T08:05:20.000+08:00|        550.0|
|1970-01-02T08:08:01.000+08:00|root.ln.wf02.wt01|1970-01-02T08:08:05.000+08:00|       1650.0|
+-----------------------------+-----------------+-----------------------------+-------------+
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><h4 id="aggregation-by-count" tabindex="-1"><a class="header-anchor" href="#aggregation-by-count"><span>Aggregation By Count</span></a></h4><p><code>GROUP BY COUNT</code>can aggregate the data points according to the number of points. It can group fixed number of continuous data points together for aggregation query.<br> Its syntax is defined as follows:</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">group</span> <span class="token keyword">by</span> <span class="token function">count</span><span class="token punctuation">(</span>controlExpression<span class="token punctuation">,</span> size<span class="token punctuation">[</span><span class="token punctuation">,</span>ignoreNull<span class="token operator">=</span><span class="token boolean">true</span><span class="token operator">/</span><span class="token boolean">false</span><span class="token punctuation">]</span><span class="token punctuation">)</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><ul><li>controlExpression</li></ul><p>The object to count during processing, it can be any column or an expression of columns.</p><ul><li>size</li></ul><p>The number of data points in a group, a number of <code>size</code> continuous points will be divided to the same group.</p><ul><li>ignoreNull=true/false</li></ul><p>Whether to ignore the data points with null in <code>controlExpression</code>, when ignoreNull is true, data points with the <code>controlExpression</code> of null will be skipped during counting.</p><h5 id="precautions-for-use-3" tabindex="-1"><a class="header-anchor" href="#precautions-for-use-3"><span>Precautions for Use</span></a></h5><ol><li>For a group in resultSet, the time column output the start time of the group by default. __endTime can be used in select clause to output the endTime of groups in resultSet.</li><li>Each device is grouped separately when used with <code>ALIGN BY DEVICE</code>.</li><li>Currently <code>GROUP BY SESSION</code> is not supported with <code>GROUP BY LEVEL</code>.</li><li>When the final number of data points in a group is less than <code>size</code>, the result of the group will not be output.</li></ol><p>For the data below, some examples will be given.</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>+-----------------------------+-----------+-----------------------+
|                         Time|root.sg.soc|root.sg.charging_status|
+-----------------------------+-----------+-----------------------+
|1970-01-01T08:00:00.001+08:00|       14.0|                      1|                                   
|1970-01-01T08:00:00.002+08:00|       16.0|                      1|                                 
|1970-01-01T08:00:00.003+08:00|       16.0|                      0|                                   
|1970-01-01T08:00:00.004+08:00|       16.0|                      0|                                   
|1970-01-01T08:00:00.005+08:00|       18.0|                      1|                                   
|1970-01-01T08:00:00.006+08:00|       24.0|                      1|                                   
|1970-01-01T08:00:00.007+08:00|       36.0|                      1|                                   
|1970-01-01T08:00:00.008+08:00|       36.0|                   null|                                   
|1970-01-01T08:00:00.009+08:00|       45.0|                      1|                                   
|1970-01-01T08:00:00.010+08:00|       60.0|                      1|
+-----------------------------+-----------+-----------------------+
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>The sql is shown below</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> <span class="token function">count</span><span class="token punctuation">(</span>charging_stauts<span class="token punctuation">)</span><span class="token punctuation">,</span> first_value<span class="token punctuation">(</span>soc<span class="token punctuation">)</span> <span class="token keyword">from</span> root<span class="token punctuation">.</span>sg <span class="token keyword">group</span> <span class="token keyword">by</span> <span class="token function">count</span><span class="token punctuation">(</span>charging_status<span class="token punctuation">,</span><span class="token number">5</span><span class="token punctuation">)</span> 
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>Get the result below, in the second group from 1970-01-01T08:00:00.006+08:00 to 1970-01-01T08:00:00.010+08:00. There are only four points included which is less than <code>size</code>. So it won&#39;t be output.</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>+-----------------------------+-----------------------------+--------------------------------------+
|                         Time|                    __endTime|first_value(root.sg.beijing.car01.soc)|
+-----------------------------+-----------------------------+--------------------------------------+
|1970-01-01T08:00:00.001+08:00|1970-01-01T08:00:00.005+08:00|                                  14.0|
+-----------------------------+-----------------------------+--------------------------------------+
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>When <code>ignoreNull=false</code> is used to take null value into account. There will be two groups with 5 points in the resultSet, which is shown as follows:</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> <span class="token function">count</span><span class="token punctuation">(</span>charging_stauts<span class="token punctuation">)</span><span class="token punctuation">,</span> first_value<span class="token punctuation">(</span>soc<span class="token punctuation">)</span> <span class="token keyword">from</span> root<span class="token punctuation">.</span>sg <span class="token keyword">group</span> <span class="token keyword">by</span> <span class="token function">count</span><span class="token punctuation">(</span>charging_status<span class="token punctuation">,</span><span class="token number">5</span><span class="token punctuation">,</span>ignoreNull<span class="token operator">=</span><span class="token boolean">false</span><span class="token punctuation">)</span> 
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>Get the results:</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>+-----------------------------+-----------------------------+--------------------------------------+
|                         Time|                    __endTime|first_value(root.sg.beijing.car01.soc)|
+-----------------------------+-----------------------------+--------------------------------------+
|1970-01-01T08:00:00.001+08:00|1970-01-01T08:00:00.005+08:00|                                  14.0|
|1970-01-01T08:00:00.006+08:00|1970-01-01T08:00:00.010+08:00|                                  24.0|
+-----------------------------+-----------------------------+--------------------------------------+
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><h3 id="aggregate-by-group" tabindex="-1"><a class="header-anchor" href="#aggregate-by-group"><span>Aggregate By Group</span></a></h3><h4 id="aggregation-by-level" tabindex="-1"><a class="header-anchor" href="#aggregation-by-level"><span>Aggregation By Level</span></a></h4><p>Aggregation by level statement is used to group the query result whose name is the same at the given level.</p><ul><li>Keyword <code>LEVEL</code> is used to specify the level that need to be grouped. By convention, <code>level=0</code> represents <em>root</em> level.</li><li>All aggregation functions are supported. When using five aggregations: sum, avg, min_value, max_value and extreme, please make sure all the aggregated series have exactly the same data type. Otherwise, it will generate a syntax error.</li></ul><p><strong>Example 1:</strong> there are multiple series named <code>status</code> under different databases， like &quot;root.ln.wf01.wt01.status&quot;, &quot;root.ln.wf02.wt02.status&quot;, and &quot;root.sgcc.wf03.wt01.status&quot;. If you need to count the number of data points of the <code>status</code> sequence under different databases, use the following query:</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> <span class="token function">count</span><span class="token punctuation">(</span><span class="token keyword">status</span><span class="token punctuation">)</span> <span class="token keyword">from</span> root<span class="token punctuation">.</span><span class="token operator">*</span><span class="token operator">*</span> <span class="token keyword">group</span> <span class="token keyword">by</span> <span class="token keyword">level</span> <span class="token operator">=</span> <span class="token number">1</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>Result：</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>+-------------------------+---------------------------+
|count(root.ln.*.*.status)|count(root.sgcc.*.*.status)|
+-------------------------+---------------------------+
|                    20160|                      10080|
+-------------------------+---------------------------+
Total line number = 1
It costs 0.003s
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p><strong>Example 2:</strong> If you need to count the number of data points under different devices, you can specify level = 3,</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> <span class="token function">count</span><span class="token punctuation">(</span><span class="token keyword">status</span><span class="token punctuation">)</span> <span class="token keyword">from</span> root<span class="token punctuation">.</span><span class="token operator">*</span><span class="token operator">*</span> <span class="token keyword">group</span> <span class="token keyword">by</span> <span class="token keyword">level</span> <span class="token operator">=</span> <span class="token number">3</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>Result：</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>+---------------------------+---------------------------+
|count(root.*.*.wt01.status)|count(root.*.*.wt02.status)|
+---------------------------+---------------------------+
|                      20160|                      10080|
+---------------------------+---------------------------+
Total line number = 1
It costs 0.003s
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p><strong>Example 3:</strong> Attention，the devices named <code>wt01</code> under databases <code>ln</code> and <code>sgcc</code> are grouped together, since they are regarded as devices with the same name. If you need to further count the number of data points in different devices under different databases, you can use the following query:</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> <span class="token function">count</span><span class="token punctuation">(</span><span class="token keyword">status</span><span class="token punctuation">)</span> <span class="token keyword">from</span> root<span class="token punctuation">.</span><span class="token operator">*</span><span class="token operator">*</span> <span class="token keyword">group</span> <span class="token keyword">by</span> <span class="token keyword">level</span> <span class="token operator">=</span> <span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">3</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>Result：</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>+----------------------------+----------------------------+------------------------------+
|count(root.ln.*.wt01.status)|count(root.ln.*.wt02.status)|count(root.sgcc.*.wt01.status)|
+----------------------------+----------------------------+------------------------------+
|                       10080|                       10080|                         10080|
+----------------------------+----------------------------+------------------------------+
Total line number = 1
It costs 0.003s
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p><strong>Example 4:</strong> Assuming that you want to query the maximum value of temperature sensor under all time series, you can use the following query statement:</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> max_value<span class="token punctuation">(</span>temperature<span class="token punctuation">)</span> <span class="token keyword">from</span> root<span class="token punctuation">.</span><span class="token operator">*</span><span class="token operator">*</span> <span class="token keyword">group</span> <span class="token keyword">by</span> <span class="token keyword">level</span> <span class="token operator">=</span> <span class="token number">0</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>Result：</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>+---------------------------------+
|max_value(root.*.*.*.temperature)|
+---------------------------------+
|                             26.0|
+---------------------------------+
Total line number = 1
It costs 0.013s
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p><strong>Example 5:</strong> The above queries are for a certain sensor. In particular, <strong>if you want to query the total data points owned by all sensors at a certain level</strong>, you need to explicitly specify <code>*</code> is selected.</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> <span class="token function">count</span><span class="token punctuation">(</span><span class="token operator">*</span><span class="token punctuation">)</span> <span class="token keyword">from</span> root<span class="token punctuation">.</span>ln<span class="token punctuation">.</span><span class="token operator">*</span><span class="token operator">*</span> <span class="token keyword">group</span> <span class="token keyword">by</span> <span class="token keyword">level</span> <span class="token operator">=</span> <span class="token number">2</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>Result：</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>+----------------------+----------------------+
|count(root.*.wf01.*.*)|count(root.*.wf02.*.*)|
+----------------------+----------------------+
|                 20160|                 20160|
+----------------------+----------------------+
Total line number = 1
It costs 0.013s
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><h5 id="aggregate-by-time-with-level-clause" tabindex="-1"><a class="header-anchor" href="#aggregate-by-time-with-level-clause"><span>Aggregate By Time with Level Clause</span></a></h5><p>Level could be defined to show count the number of points of each node at the given level in current Metadata Tree.</p><p>This could be used to query the number of points under each device.</p><p>The SQL statement is:</p><p>Get time aggregation by level.</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> <span class="token function">count</span><span class="token punctuation">(</span><span class="token keyword">status</span><span class="token punctuation">)</span> <span class="token keyword">from</span> root<span class="token punctuation">.</span>ln<span class="token punctuation">.</span>wf01<span class="token punctuation">.</span>wt01 <span class="token keyword">group</span> <span class="token keyword">by</span> <span class="token punctuation">(</span><span class="token punctuation">(</span><span class="token number">2017</span><span class="token operator">-</span><span class="token number">11</span><span class="token operator">-</span><span class="token number">01</span>T00:<span class="token number">00</span>:<span class="token number">00</span><span class="token punctuation">,</span> <span class="token number">2017</span><span class="token operator">-</span><span class="token number">11</span><span class="token operator">-</span><span class="token number">07</span>T23:<span class="token number">00</span>:<span class="token number">00</span><span class="token punctuation">]</span><span class="token punctuation">,</span><span class="token number">1</span>d<span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token keyword">level</span><span class="token operator">=</span><span class="token number">1</span><span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>Result:</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>+-----------------------------+-------------------------+
|                         Time|COUNT(root.ln.*.*.status)|
+-----------------------------+-------------------------+
|2017-11-02T00:00:00.000+08:00|                     1440|
|2017-11-03T00:00:00.000+08:00|                     1440|
|2017-11-04T00:00:00.000+08:00|                     1440|
|2017-11-05T00:00:00.000+08:00|                     1440|
|2017-11-06T00:00:00.000+08:00|                     1440|
|2017-11-07T00:00:00.000+08:00|                     1440|
|2017-11-07T23:00:00.000+08:00|                     1380|
+-----------------------------+-------------------------+
Total line number = 7
It costs 0.006s
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>Time aggregation with sliding step and by level.</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> <span class="token function">count</span><span class="token punctuation">(</span><span class="token keyword">status</span><span class="token punctuation">)</span> <span class="token keyword">from</span> root<span class="token punctuation">.</span>ln<span class="token punctuation">.</span>wf01<span class="token punctuation">.</span>wt01 <span class="token keyword">group</span> <span class="token keyword">by</span> <span class="token punctuation">(</span><span class="token punctuation">[</span><span class="token number">2017</span><span class="token operator">-</span><span class="token number">11</span><span class="token operator">-</span><span class="token number">01</span> <span class="token number">00</span>:<span class="token number">00</span>:<span class="token number">00</span><span class="token punctuation">,</span> <span class="token number">2017</span><span class="token operator">-</span><span class="token number">11</span><span class="token operator">-</span><span class="token number">07</span> <span class="token number">23</span>:<span class="token number">00</span>:<span class="token number">00</span><span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token number">3</span>h<span class="token punctuation">,</span> <span class="token number">1</span>d<span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token keyword">level</span><span class="token operator">=</span><span class="token number">1</span><span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>Result:</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>+-----------------------------+-------------------------+
|                         Time|COUNT(root.ln.*.*.status)|
+-----------------------------+-------------------------+
|2017-11-01T00:00:00.000+08:00|                      180|
|2017-11-02T00:00:00.000+08:00|                      180|
|2017-11-03T00:00:00.000+08:00|                      180|
|2017-11-04T00:00:00.000+08:00|                      180|
|2017-11-05T00:00:00.000+08:00|                      180|
|2017-11-06T00:00:00.000+08:00|                      180|
|2017-11-07T00:00:00.000+08:00|                      180|
+-----------------------------+-------------------------+
Total line number = 7
It costs 0.004s
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><h4 id="aggregation-by-tags" tabindex="-1"><a class="header-anchor" href="#aggregation-by-tags"><span>Aggregation By Tags</span></a></h4><p>IotDB allows you to do aggregation query with the tags defined in timeseries through <code>GROUP BY TAGS</code> clause as well.</p><p>Firstly, we can put these example data into IoTDB, which will be used in the following feature introduction.</p><p>These are the temperature data of the workshops, which belongs to the factory <code>factory1</code> and locates in different cities. The time range is <code>[1000, 10000)</code>.</p><p>The device node of the timeseries path is the ID of the device. The information of city and workshop are modelled in the tags <code>city</code> and <code>workshop</code>.<br> The devices <code>d1</code> and <code>d2</code> belong to the workshop <code>d1</code> in <code>Beijing</code>.<br><code>d3</code> and <code>d4</code> belong to the workshop <code>w2</code> in <code>Beijing</code>.<br><code>d5</code> and <code>d6</code> belong to the workshop <code>w1</code> in <code>Shanghai</code>.<br><code>d7</code> belongs to the workshop <code>w2</code> in <code>Shanghai</code>.<br><code>d8</code> and <code>d9</code> are under maintenance, and don&#39;t belong to any workshops, so they have no tags.</p><div class="language-SQL line-numbers-mode" data-ext="SQL" data-title="SQL"><pre class="language-SQL"><code>CREATE DATABASE root.factory1;
create timeseries root.factory1.d1.temperature with datatype=FLOAT tags(city=Beijing, workshop=w1);
create timeseries root.factory1.d2.temperature with datatype=FLOAT tags(city=Beijing, workshop=w1);
create timeseries root.factory1.d3.temperature with datatype=FLOAT tags(city=Beijing, workshop=w2);
create timeseries root.factory1.d4.temperature with datatype=FLOAT tags(city=Beijing, workshop=w2);
create timeseries root.factory1.d5.temperature with datatype=FLOAT tags(city=Shanghai, workshop=w1);
create timeseries root.factory1.d6.temperature with datatype=FLOAT tags(city=Shanghai, workshop=w1);
create timeseries root.factory1.d7.temperature with datatype=FLOAT tags(city=Shanghai, workshop=w2);
create timeseries root.factory1.d8.temperature with datatype=FLOAT;
create timeseries root.factory1.d9.temperature with datatype=FLOAT;

insert into root.factory1.d1(time, temperature) values(1000, 104.0);
insert into root.factory1.d1(time, temperature) values(3000, 104.2);
insert into root.factory1.d1(time, temperature) values(5000, 103.3);
insert into root.factory1.d1(time, temperature) values(7000, 104.1);

insert into root.factory1.d2(time, temperature) values(1000, 104.4);
insert into root.factory1.d2(time, temperature) values(3000, 103.7);
insert into root.factory1.d2(time, temperature) values(5000, 103.3);
insert into root.factory1.d2(time, temperature) values(7000, 102.9);

insert into root.factory1.d3(time, temperature) values(1000, 103.9);
insert into root.factory1.d3(time, temperature) values(3000, 103.8);
insert into root.factory1.d3(time, temperature) values(5000, 102.7);
insert into root.factory1.d3(time, temperature) values(7000, 106.9);

insert into root.factory1.d4(time, temperature) values(1000, 103.9);
insert into root.factory1.d4(time, temperature) values(5000, 102.7);
insert into root.factory1.d4(time, temperature) values(7000, 106.9);

insert into root.factory1.d5(time, temperature) values(1000, 112.9);
insert into root.factory1.d5(time, temperature) values(7000, 113.0);

insert into root.factory1.d6(time, temperature) values(1000, 113.9);
insert into root.factory1.d6(time, temperature) values(3000, 113.3);
insert into root.factory1.d6(time, temperature) values(5000, 112.7);
insert into root.factory1.d6(time, temperature) values(7000, 112.3);

insert into root.factory1.d7(time, temperature) values(1000, 101.2);
insert into root.factory1.d7(time, temperature) values(3000, 99.3);
insert into root.factory1.d7(time, temperature) values(5000, 100.1);
insert into root.factory1.d7(time, temperature) values(7000, 99.8);

insert into root.factory1.d8(time, temperature) values(1000, 50.0);
insert into root.factory1.d8(time, temperature) values(3000, 52.1);
insert into root.factory1.d8(time, temperature) values(5000, 50.1);
insert into root.factory1.d8(time, temperature) values(7000, 50.5);

insert into root.factory1.d9(time, temperature) values(1000, 50.3);
insert into root.factory1.d9(time, temperature) values(3000, 52.1);
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><h5 id="aggregation-query-by-one-single-tag" tabindex="-1"><a class="header-anchor" href="#aggregation-query-by-one-single-tag"><span>Aggregation query by one single tag</span></a></h5><p>If the user wants to know the average temperature of each workshop, he can query like this</p><div class="language-SQL line-numbers-mode" data-ext="SQL" data-title="SQL"><pre class="language-SQL"><code>SELECT AVG(temperature) FROM root.factory1.** GROUP BY TAGS(city);
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>The query will calculate the average of the temperatures of those timeseries which have the same tag value of the key <code>city</code>.<br> The results are</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>+--------+------------------+
|    city|  avg(temperature)|
+--------+------------------+
| Beijing|104.04666697184244|
|Shanghai|107.85000076293946|
|    NULL| 50.84999910990397|
+--------+------------------+
Total line number = 3
It costs 0.231s
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>From the results we can see that the differences between aggregation by tags query and aggregation by time or level query are:</p><ol><li>Aggregation query by tags will no longer remove wildcard to raw timeseries, but do the aggregation through the data of multiple timeseries, which have the same tag value.</li><li>Except for the aggregate result column, the result set contains the key-value column of the grouped tag. The column name is the tag key, and the values in the column are tag values which present in the searched timeseries.<br> If some searched timeseries doesn&#39;t have the grouped tag, a <code>NULL</code> value in the key-value column of the grouped tag will be presented, which means the aggregation of all the timeseries lacking the tagged key.</li></ol><h5 id="aggregation-query-by-multiple-tags" tabindex="-1"><a class="header-anchor" href="#aggregation-query-by-multiple-tags"><span>Aggregation query by multiple tags</span></a></h5><p>Except for the aggregation query by one single tag, aggregation query by multiple tags in a particular order is allowed as well.</p><p>For example, a user wants to know the average temperature of the devices in each workshop.<br> As the workshop names may be same in different city, it&#39;s not correct to aggregated by the tag <code>workshop</code> directly.<br> So the aggregation by the tag <code>city</code> should be done first, and then by the tag <code>workshop</code>.</p><p>SQL</p><div class="language-SQL line-numbers-mode" data-ext="SQL" data-title="SQL"><pre class="language-SQL"><code>SELECT avg(temperature) FROM root.factory1.** GROUP BY TAGS(city, workshop);
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>The results</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>+--------+--------+------------------+
|    city|workshop|  avg(temperature)|
+--------+--------+------------------+
|    NULL|    NULL| 50.84999910990397|
|Shanghai|      w1|113.01666768391927|
| Beijing|      w2| 104.4000004359654|
|Shanghai|      w2|100.10000038146973|
| Beijing|      w1|103.73750019073486|
+--------+--------+------------------+
Total line number = 5
It costs 0.027s
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>We can see that in a multiple tags aggregation query, the result set will output the key-value columns of all the grouped tag keys, which have the same order with the one in <code>GROUP BY TAGS</code>.</p><h5 id="downsampling-aggregation-by-tags-based-on-time-window" tabindex="-1"><a class="header-anchor" href="#downsampling-aggregation-by-tags-based-on-time-window"><span>Downsampling Aggregation by tags based on Time Window</span></a></h5><p>Downsampling aggregation by time window is one of the most popular features in a time series database. IoTDB supports to do aggregation query by tags based on time window.</p><p>For example, a user wants to know the average temperature of the devices in each workshop, in every 5 seconds, in the range of time <code>[1000, 10000)</code>.</p><p>SQL</p><div class="language-SQL line-numbers-mode" data-ext="SQL" data-title="SQL"><pre class="language-SQL"><code>SELECT avg(temperature) FROM root.factory1.** GROUP BY ([1000, 10000), 5s), TAGS(city, workshop);
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>The results</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>+-----------------------------+--------+--------+------------------+
|                         Time|    city|workshop|  avg(temperature)|
+-----------------------------+--------+--------+------------------+
|1970-01-01T08:00:01.000+08:00|    NULL|    NULL| 50.91999893188476|
|1970-01-01T08:00:01.000+08:00|Shanghai|      w1|113.20000076293945|
|1970-01-01T08:00:01.000+08:00| Beijing|      w2|             103.4|
|1970-01-01T08:00:01.000+08:00|Shanghai|      w2| 100.1999994913737|
|1970-01-01T08:00:01.000+08:00| Beijing|      w1|103.81666692097981|
|1970-01-01T08:00:06.000+08:00|    NULL|    NULL|              50.5|
|1970-01-01T08:00:06.000+08:00|Shanghai|      w1| 112.6500015258789|
|1970-01-01T08:00:06.000+08:00| Beijing|      w2| 106.9000015258789|
|1970-01-01T08:00:06.000+08:00|Shanghai|      w2| 99.80000305175781|
|1970-01-01T08:00:06.000+08:00| Beijing|      w1|             103.5|
+-----------------------------+--------+--------+------------------+
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>Comparing to the pure tag aggregations, this kind of aggregation will divide the data according to the time window specification firstly, and do the aggregation query by the multiple tags in each time window secondly.<br> The result set will also contain a time column, which have the same meaning with the time column of the result in downsampling aggregation query by time window.</p><h5 id="limitation-of-aggregation-by-tags" tabindex="-1"><a class="header-anchor" href="#limitation-of-aggregation-by-tags"><span>Limitation of Aggregation by Tags</span></a></h5><p>As this feature is still under development, some queries have not been completed yet and will be supported in the future.</p><blockquote><ol><li>Temporarily not support <code>HAVING</code> clause to filter the results.</li><li>Temporarily not support ordering by tag values.</li><li>Temporarily not support <code>LIMIT</code>，<code>OFFSET</code>，<code>SLIMIT</code>，<code>SOFFSET</code>.</li><li>Temporarily not support <code>ALIGN BY DEVICE</code>.</li><li>Temporarily not support expressions as aggregation function parameter，e.g. <code>count(s+1)</code>.</li><li>Not support the value filter, which stands the same with the <code>GROUP BY LEVEL</code> query.</li></ol></blockquote><h2 id="having-clause-1" tabindex="-1"><a class="header-anchor" href="#having-clause-1"><span><code>HAVING</code> CLAUSE</span></a></h2><p>If you want to filter the results of aggregate queries,<br> you can use the <code>HAVING</code> clause after the <code>GROUP BY</code> clause.</p><blockquote><p>NOTE：</p><p>1.The expression in HAVING clause must consist of aggregate values; the original sequence cannot appear alone.<br> The following usages are incorrect:</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> <span class="token function">count</span><span class="token punctuation">(</span>s1<span class="token punctuation">)</span> <span class="token keyword">from</span> root<span class="token punctuation">.</span><span class="token operator">*</span><span class="token operator">*</span> <span class="token keyword">group</span> <span class="token keyword">by</span> <span class="token punctuation">(</span><span class="token punctuation">[</span><span class="token number">1</span><span class="token punctuation">,</span><span class="token number">3</span><span class="token punctuation">)</span><span class="token punctuation">,</span><span class="token number">1</span>ms<span class="token punctuation">)</span> <span class="token keyword">having</span> <span class="token function">sum</span><span class="token punctuation">(</span>s1<span class="token punctuation">)</span> <span class="token operator">&gt;</span> s1
<span class="token keyword">select</span> <span class="token function">count</span><span class="token punctuation">(</span>s1<span class="token punctuation">)</span> <span class="token keyword">from</span> root<span class="token punctuation">.</span><span class="token operator">*</span><span class="token operator">*</span> <span class="token keyword">group</span> <span class="token keyword">by</span> <span class="token punctuation">(</span><span class="token punctuation">[</span><span class="token number">1</span><span class="token punctuation">,</span><span class="token number">3</span><span class="token punctuation">)</span><span class="token punctuation">,</span><span class="token number">1</span>ms<span class="token punctuation">)</span> <span class="token keyword">having</span> s1 <span class="token operator">&gt;</span> <span class="token number">1</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div></div></div><p>2.When filtering the <code>GROUP BY LEVEL</code> result, the PATH in <code>SELECT</code> and <code>HAVING</code> can only have one node.<br> The following usages are incorrect:</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> <span class="token function">count</span><span class="token punctuation">(</span>s1<span class="token punctuation">)</span> <span class="token keyword">from</span> root<span class="token punctuation">.</span><span class="token operator">*</span><span class="token operator">*</span> <span class="token keyword">group</span> <span class="token keyword">by</span> <span class="token punctuation">(</span><span class="token punctuation">[</span><span class="token number">1</span><span class="token punctuation">,</span><span class="token number">3</span><span class="token punctuation">)</span><span class="token punctuation">,</span><span class="token number">1</span>ms<span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token keyword">level</span><span class="token operator">=</span><span class="token number">1</span> <span class="token keyword">having</span> <span class="token function">sum</span><span class="token punctuation">(</span>d1<span class="token punctuation">.</span>s1<span class="token punctuation">)</span> <span class="token operator">&gt;</span> <span class="token number">1</span>
<span class="token keyword">select</span> <span class="token function">count</span><span class="token punctuation">(</span>d1<span class="token punctuation">.</span>s1<span class="token punctuation">)</span> <span class="token keyword">from</span> root<span class="token punctuation">.</span><span class="token operator">*</span><span class="token operator">*</span> <span class="token keyword">group</span> <span class="token keyword">by</span> <span class="token punctuation">(</span><span class="token punctuation">[</span><span class="token number">1</span><span class="token punctuation">,</span><span class="token number">3</span><span class="token punctuation">)</span><span class="token punctuation">,</span><span class="token number">1</span>ms<span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token keyword">level</span><span class="token operator">=</span><span class="token number">1</span> <span class="token keyword">having</span> <span class="token function">sum</span><span class="token punctuation">(</span>s1<span class="token punctuation">)</span> <span class="token operator">&gt;</span> <span class="token number">1</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div></div></div></blockquote><p>Here are a few examples of using the &#39;HAVING&#39; clause to filter aggregate results.</p><p>Aggregation result 1：</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>+-----------------------------+---------------------+---------------------+
|                         Time|count(root.test.*.s1)|count(root.test.*.s2)|
+-----------------------------+---------------------+---------------------+
|1970-01-01T08:00:00.001+08:00|                    4|                    4|
|1970-01-01T08:00:00.003+08:00|                    1|                    0|
|1970-01-01T08:00:00.005+08:00|                    2|                    4|
|1970-01-01T08:00:00.007+08:00|                    3|                    2|
|1970-01-01T08:00:00.009+08:00|                    4|                    4|
+-----------------------------+---------------------+---------------------+
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>Aggregation result filtering query 1：</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code> <span class="token keyword">select</span> <span class="token function">count</span><span class="token punctuation">(</span>s1<span class="token punctuation">)</span> <span class="token keyword">from</span> root<span class="token punctuation">.</span><span class="token operator">*</span><span class="token operator">*</span> <span class="token keyword">group</span> <span class="token keyword">by</span> <span class="token punctuation">(</span><span class="token punctuation">[</span><span class="token number">1</span><span class="token punctuation">,</span><span class="token number">11</span><span class="token punctuation">)</span><span class="token punctuation">,</span><span class="token number">2</span>ms<span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token keyword">level</span><span class="token operator">=</span><span class="token number">1</span> <span class="token keyword">having</span> <span class="token function">count</span><span class="token punctuation">(</span>s2<span class="token punctuation">)</span> <span class="token operator">&gt;</span> <span class="token number">1</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>Filtering result 1：</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>+-----------------------------+---------------------+
|                         Time|count(root.test.*.s1)|
+-----------------------------+---------------------+
|1970-01-01T08:00:00.001+08:00|                    4|
|1970-01-01T08:00:00.005+08:00|                    2|
|1970-01-01T08:00:00.009+08:00|                    4|
+-----------------------------+---------------------+
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>Aggregation result 2：</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>+-----------------------------+-------------+---------+---------+
|                         Time|       Device|count(s1)|count(s2)|
+-----------------------------+-------------+---------+---------+
|1970-01-01T08:00:00.001+08:00|root.test.sg1|        1|        2|
|1970-01-01T08:00:00.003+08:00|root.test.sg1|        1|        0|
|1970-01-01T08:00:00.005+08:00|root.test.sg1|        1|        2|
|1970-01-01T08:00:00.007+08:00|root.test.sg1|        2|        1|
|1970-01-01T08:00:00.009+08:00|root.test.sg1|        2|        2|
|1970-01-01T08:00:00.001+08:00|root.test.sg2|        2|        2|
|1970-01-01T08:00:00.003+08:00|root.test.sg2|        0|        0|
|1970-01-01T08:00:00.005+08:00|root.test.sg2|        1|        2|
|1970-01-01T08:00:00.007+08:00|root.test.sg2|        1|        1|
|1970-01-01T08:00:00.009+08:00|root.test.sg2|        2|        2|
+-----------------------------+-------------+---------+---------+
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>Aggregation result filtering query 2：</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code> <span class="token keyword">select</span> <span class="token function">count</span><span class="token punctuation">(</span>s1<span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token function">count</span><span class="token punctuation">(</span>s2<span class="token punctuation">)</span> <span class="token keyword">from</span> root<span class="token punctuation">.</span><span class="token operator">*</span><span class="token operator">*</span> <span class="token keyword">group</span> <span class="token keyword">by</span> <span class="token punctuation">(</span><span class="token punctuation">[</span><span class="token number">1</span><span class="token punctuation">,</span><span class="token number">11</span><span class="token punctuation">)</span><span class="token punctuation">,</span><span class="token number">2</span>ms<span class="token punctuation">)</span> <span class="token keyword">having</span> <span class="token function">count</span><span class="token punctuation">(</span>s2<span class="token punctuation">)</span> <span class="token operator">&gt;</span> <span class="token number">1</span> align <span class="token keyword">by</span> device
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>Filtering result 2：</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>+-----------------------------+-------------+---------+---------+
|                         Time|       Device|count(s1)|count(s2)|
+-----------------------------+-------------+---------+---------+
|1970-01-01T08:00:00.001+08:00|root.test.sg1|        1|        2|
|1970-01-01T08:00:00.005+08:00|root.test.sg1|        1|        2|
|1970-01-01T08:00:00.009+08:00|root.test.sg1|        2|        2|
|1970-01-01T08:00:00.001+08:00|root.test.sg2|        2|        2|
|1970-01-01T08:00:00.005+08:00|root.test.sg2|        1|        2|
|1970-01-01T08:00:00.009+08:00|root.test.sg2|        2|        2|
+-----------------------------+-------------+---------+---------+
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><h2 id="fill-clause-1" tabindex="-1"><a class="header-anchor" href="#fill-clause-1"><span><code>FILL</code> CLAUSE</span></a></h2><h3 id="introduction" tabindex="-1"><a class="header-anchor" href="#introduction"><span>Introduction</span></a></h3><p>When executing some queries, there may be no data for some columns in some rows, and data in these locations will be null, but this kind of null value is not conducive to data visualization and analysis, and the null value needs to be filled.</p><p>In IoTDB, users can use the FILL clause to specify the fill mode when data is missing. Fill null value allows the user to fill any query result with null values according to a specific method, such as taking the previous value that is not null, or linear interpolation. The query result after filling the null value can better reflect the data distribution, which is beneficial for users to perform data analysis.</p><h3 id="syntax-definition-1" tabindex="-1"><a class="header-anchor" href="#syntax-definition-1"><span>Syntax Definition</span></a></h3><p><strong>The following is the syntax definition of the <code>FILL</code> clause:</strong></p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code>FILL <span class="token string">&#39;(&#39;</span> PREVIOUS <span class="token operator">|</span> LINEAR <span class="token operator">|</span> constant <span class="token string">&#39;)&#39;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p><strong>Note:</strong></p><ul><li>We can specify only one fill method in the <code>FILL</code> clause, and this method applies to all columns of the result set.</li><li>Null value fill is not compatible with version 0.13 and previous syntax (<code>FILL((&lt;data_type&gt;[&lt;fill_method&gt;(, &lt;before_range&gt;, &lt;after_range&gt;)?])+)</code>) is not supported anymore.</li></ul><h3 id="fill-methods" tabindex="-1"><a class="header-anchor" href="#fill-methods"><span>Fill Methods</span></a></h3><p><strong>IoTDB supports the following three fill methods:</strong></p><ul><li><code>PREVIOUS</code>: Fill with the previous non-null value of the column.</li><li><code>LINEAR</code>: Fill the column with a linear interpolation of the previous non-null value and the next non-null value of the column.</li><li>Constant: Fill with the specified constant.</li></ul><p><strong>Following table lists the data types and supported fill methods.</strong></p><table><thead><tr><th style="text-align:left;">Data Type</th><th style="text-align:left;">Supported Fill Methods</th></tr></thead><tbody><tr><td style="text-align:left;">boolean</td><td style="text-align:left;">previous, value</td></tr><tr><td style="text-align:left;">int32</td><td style="text-align:left;">previous, linear, value</td></tr><tr><td style="text-align:left;">int64</td><td style="text-align:left;">previous, linear, value</td></tr><tr><td style="text-align:left;">float</td><td style="text-align:left;">previous, linear, value</td></tr><tr><td style="text-align:left;">double</td><td style="text-align:left;">previous, linear, value</td></tr><tr><td style="text-align:left;">text</td><td style="text-align:left;">previous, value</td></tr></tbody></table><p><strong>Note:</strong> For columns whose data type does not support specifying the fill method, we neither fill it nor throw exception, just keep it as it is.</p><p><strong>For examples:</strong></p><p>If we don&#39;t use any fill methods:</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> temperature<span class="token punctuation">,</span> <span class="token keyword">status</span> <span class="token keyword">from</span> root<span class="token punctuation">.</span>sgcc<span class="token punctuation">.</span>wf03<span class="token punctuation">.</span>wt01 <span class="token keyword">where</span> <span class="token keyword">time</span> <span class="token operator">&gt;=</span> <span class="token number">2017</span><span class="token operator">-</span><span class="token number">11</span><span class="token operator">-</span><span class="token number">01</span>T16:<span class="token number">37</span>:<span class="token number">00.000</span> <span class="token operator">and</span> <span class="token keyword">time</span> <span class="token operator">&lt;=</span> <span class="token number">2017</span><span class="token operator">-</span><span class="token number">11</span><span class="token operator">-</span><span class="token number">01</span>T16:<span class="token number">40</span>:<span class="token number">00.000</span><span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>the original result will be like:</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>+-----------------------------+-------------------------------+--------------------------+
|                         Time|root.sgcc.wf03.wt01.temperature|root.sgcc.wf03.wt01.status|
+-----------------------------+-------------------------------+--------------------------+
|2017-11-01T16:37:00.000+08:00|                          21.93|                      true|
+-----------------------------+-------------------------------+--------------------------+
|2017-11-01T16:38:00.000+08:00|                           null|                     false|
+-----------------------------+-------------------------------+--------------------------+
|2017-11-01T16:39:00.000+08:00|                          22.23|                      null|
+-----------------------------+-------------------------------+--------------------------+
|2017-11-01T16:40:00.000+08:00|                          23.43|                      null|
+-----------------------------+-------------------------------+--------------------------+
Total line number = 4
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><h4 id="previous-fill" tabindex="-1"><a class="header-anchor" href="#previous-fill"><span><code>PREVIOUS</code> Fill</span></a></h4><p><strong>For null values in the query result set, fill with the previous non-null value of the column.</strong></p><p><strong>Note:</strong> If the first value of this column is null, we will keep first value as null and won&#39;t fill it until we meet first non-null value</p><p>For example, with <code>PREVIOUS</code> fill, the SQL is as follows:</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> temperature<span class="token punctuation">,</span> <span class="token keyword">status</span> <span class="token keyword">from</span> root<span class="token punctuation">.</span>sgcc<span class="token punctuation">.</span>wf03<span class="token punctuation">.</span>wt01 <span class="token keyword">where</span> <span class="token keyword">time</span> <span class="token operator">&gt;=</span> <span class="token number">2017</span><span class="token operator">-</span><span class="token number">11</span><span class="token operator">-</span><span class="token number">01</span>T16:<span class="token number">37</span>:<span class="token number">00.000</span> <span class="token operator">and</span> <span class="token keyword">time</span> <span class="token operator">&lt;=</span> <span class="token number">2017</span><span class="token operator">-</span><span class="token number">11</span><span class="token operator">-</span><span class="token number">01</span>T16:<span class="token number">40</span>:<span class="token number">00.000</span> fill<span class="token punctuation">(</span>previous<span class="token punctuation">)</span><span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>result will be like:</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>+-----------------------------+-------------------------------+--------------------------+
|                         Time|root.sgcc.wf03.wt01.temperature|root.sgcc.wf03.wt01.status|
+-----------------------------+-------------------------------+--------------------------+
|2017-11-01T16:37:00.000+08:00|                          21.93|                      true|
+-----------------------------+-------------------------------+--------------------------+
|2017-11-01T16:38:00.000+08:00|                          21.93|                     false|
+-----------------------------+-------------------------------+--------------------------+
|2017-11-01T16:39:00.000+08:00|                          22.23|                     false|
+-----------------------------+-------------------------------+--------------------------+
|2017-11-01T16:40:00.000+08:00|                          23.43|                     false|
+-----------------------------+-------------------------------+--------------------------+
Total line number = 4
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><h4 id="linear-fill" tabindex="-1"><a class="header-anchor" href="#linear-fill"><span><code>LINEAR</code> Fill</span></a></h4><p><strong>For null values in the query result set, fill the column with a linear interpolation of the previous non-null value and the next non-null value of the column.</strong></p><p><strong>Note:</strong></p><ul><li>If all the values before current value are null or all the values after current value are null, we will keep current value as null and won&#39;t fill it.</li><li>If the column&#39;s data type is boolean/text, we neither fill it nor throw exception, just keep it as it is.</li></ul><p>Here we give an example of filling null values using the linear method. The SQL statement is as follows:</p><p>For example, with <code>LINEAR</code> fill, the SQL is as follows:</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> temperature<span class="token punctuation">,</span> <span class="token keyword">status</span> <span class="token keyword">from</span> root<span class="token punctuation">.</span>sgcc<span class="token punctuation">.</span>wf03<span class="token punctuation">.</span>wt01 <span class="token keyword">where</span> <span class="token keyword">time</span> <span class="token operator">&gt;=</span> <span class="token number">2017</span><span class="token operator">-</span><span class="token number">11</span><span class="token operator">-</span><span class="token number">01</span>T16:<span class="token number">37</span>:<span class="token number">00.000</span> <span class="token operator">and</span> <span class="token keyword">time</span> <span class="token operator">&lt;=</span> <span class="token number">2017</span><span class="token operator">-</span><span class="token number">11</span><span class="token operator">-</span><span class="token number">01</span>T16:<span class="token number">40</span>:<span class="token number">00.000</span> fill<span class="token punctuation">(</span>linear<span class="token punctuation">)</span><span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>result will be like:</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>+-----------------------------+-------------------------------+--------------------------+
|                         Time|root.sgcc.wf03.wt01.temperature|root.sgcc.wf03.wt01.status|
+-----------------------------+-------------------------------+--------------------------+
|2017-11-01T16:37:00.000+08:00|                          21.93|                      true|
+-----------------------------+-------------------------------+--------------------------+
|2017-11-01T16:38:00.000+08:00|                          22.08|                     false|
+-----------------------------+-------------------------------+--------------------------+
|2017-11-01T16:39:00.000+08:00|                          22.23|                      null|
+-----------------------------+-------------------------------+--------------------------+
|2017-11-01T16:40:00.000+08:00|                          23.43|                      null|
+-----------------------------+-------------------------------+--------------------------+
Total line number = 4
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><h4 id="constant-fill" tabindex="-1"><a class="header-anchor" href="#constant-fill"><span>Constant Fill</span></a></h4><p><strong>For null values in the query result set, fill with the specified constant.</strong></p><p><strong>Note:</strong></p><ul><li><p>When using the ValueFill, IoTDB neither fill the query result if the data type is different from the input constant nor throw exception, just keep it as it is.</p><table><thead><tr><th style="text-align:left;">Constant Value Data Type</th><th style="text-align:left;">Support Data Type</th></tr></thead><tbody><tr><td style="text-align:left;"><code>BOOLEAN</code></td><td style="text-align:left;"><code>BOOLEAN</code> <code>TEXT</code></td></tr><tr><td style="text-align:left;"><code>INT64</code></td><td style="text-align:left;"><code>INT32</code> <code>INT64</code> <code>FLOAT</code> <code>DOUBLE</code> <code>TEXT</code></td></tr><tr><td style="text-align:left;"><code>DOUBLE</code></td><td style="text-align:left;"><code>FLOAT</code> <code>DOUBLE</code> <code>TEXT</code></td></tr><tr><td style="text-align:left;"><code>TEXT</code></td><td style="text-align:left;"><code>TEXT</code></td></tr></tbody></table></li><li><p>If constant value is larger than Integer.MAX_VALUE, IoTDB neither fill the query result if the data type is int32 nor throw exception, just keep it as it is.</p></li></ul><p>For example, with <code>FLOAT</code> constant fill, the SQL is as follows:</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> temperature<span class="token punctuation">,</span> <span class="token keyword">status</span> <span class="token keyword">from</span> root<span class="token punctuation">.</span>sgcc<span class="token punctuation">.</span>wf03<span class="token punctuation">.</span>wt01 <span class="token keyword">where</span> <span class="token keyword">time</span> <span class="token operator">&gt;=</span> <span class="token number">2017</span><span class="token operator">-</span><span class="token number">11</span><span class="token operator">-</span><span class="token number">01</span>T16:<span class="token number">37</span>:<span class="token number">00.000</span> <span class="token operator">and</span> <span class="token keyword">time</span> <span class="token operator">&lt;=</span> <span class="token number">2017</span><span class="token operator">-</span><span class="token number">11</span><span class="token operator">-</span><span class="token number">01</span>T16:<span class="token number">40</span>:<span class="token number">00.000</span> fill<span class="token punctuation">(</span><span class="token number">2.0</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>result will be like:</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>+-----------------------------+-------------------------------+--------------------------+
|                         Time|root.sgcc.wf03.wt01.temperature|root.sgcc.wf03.wt01.status|
+-----------------------------+-------------------------------+--------------------------+
|2017-11-01T16:37:00.000+08:00|                          21.93|                      true|
+-----------------------------+-------------------------------+--------------------------+
|2017-11-01T16:38:00.000+08:00|                            2.0|                     false|
+-----------------------------+-------------------------------+--------------------------+
|2017-11-01T16:39:00.000+08:00|                          22.23|                      null|
+-----------------------------+-------------------------------+--------------------------+
|2017-11-01T16:40:00.000+08:00|                          23.43|                      null|
+-----------------------------+-------------------------------+--------------------------+
Total line number = 4
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>For example, with <code>BOOLEAN</code> constant fill, the SQL is as follows:</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> temperature<span class="token punctuation">,</span> <span class="token keyword">status</span> <span class="token keyword">from</span> root<span class="token punctuation">.</span>sgcc<span class="token punctuation">.</span>wf03<span class="token punctuation">.</span>wt01 <span class="token keyword">where</span> <span class="token keyword">time</span> <span class="token operator">&gt;=</span> <span class="token number">2017</span><span class="token operator">-</span><span class="token number">11</span><span class="token operator">-</span><span class="token number">01</span>T16:<span class="token number">37</span>:<span class="token number">00.000</span> <span class="token operator">and</span> <span class="token keyword">time</span> <span class="token operator">&lt;=</span> <span class="token number">2017</span><span class="token operator">-</span><span class="token number">11</span><span class="token operator">-</span><span class="token number">01</span>T16:<span class="token number">40</span>:<span class="token number">00.000</span> fill<span class="token punctuation">(</span><span class="token boolean">true</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>result will be like:</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>+-----------------------------+-------------------------------+--------------------------+
|                         Time|root.sgcc.wf03.wt01.temperature|root.sgcc.wf03.wt01.status|
+-----------------------------+-------------------------------+--------------------------+
|2017-11-01T16:37:00.000+08:00|                          21.93|                      true|
+-----------------------------+-------------------------------+--------------------------+
|2017-11-01T16:38:00.000+08:00|                           null|                     false|
+-----------------------------+-------------------------------+--------------------------+
|2017-11-01T16:39:00.000+08:00|                          22.23|                      true|
+-----------------------------+-------------------------------+--------------------------+
|2017-11-01T16:40:00.000+08:00|                          23.43|                      true|
+-----------------------------+-------------------------------+--------------------------+
Total line number = 4
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><h2 id="limit-and-slimit-clauses-pagination" tabindex="-1"><a class="header-anchor" href="#limit-and-slimit-clauses-pagination"><span><code>LIMIT</code> and <code>SLIMIT</code> CLAUSES (PAGINATION)</span></a></h2><p>When the query result set has a large amount of data, it is not conducive to display on one page. You can use the <code>LIMIT/SLIMIT</code> clause and the <code>OFFSET/SOFFSET</code> clause to control paging.</p><ul><li>The <code>LIMIT</code> and <code>SLIMIT</code> clauses are used to control the number of rows and columns of query results.</li><li>The <code>OFFSET</code> and <code>SOFFSET</code> clauses are used to control the starting position of the result display.</li></ul><h3 id="row-control-over-query-results" tabindex="-1"><a class="header-anchor" href="#row-control-over-query-results"><span>Row Control over Query Results</span></a></h3><p>By using LIMIT and OFFSET clauses, users control the query results in a row-related manner. We demonstrate how to use LIMIT and OFFSET clauses through the following examples.</p><ul><li>Example 1: basic LIMIT clause</li></ul><p>The SQL statement is:</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> <span class="token keyword">status</span><span class="token punctuation">,</span> temperature <span class="token keyword">from</span> root<span class="token punctuation">.</span>ln<span class="token punctuation">.</span>wf01<span class="token punctuation">.</span>wt01 <span class="token keyword">limit</span> <span class="token number">10</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>which means:</p><p>The selected device is ln group wf01 plant wt01 device; the selected timeseries is &quot;status&quot; and &quot;temperature&quot;. The SQL statement requires the first 10 rows of the query result.</p><p>The result is shown below:</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>+-----------------------------+------------------------+-----------------------------+
|                         Time|root.ln.wf01.wt01.status|root.ln.wf01.wt01.temperature|
+-----------------------------+------------------------+-----------------------------+
|2017-11-01T00:00:00.000+08:00|                    true|                        25.96|
|2017-11-01T00:01:00.000+08:00|                    true|                        24.36|
|2017-11-01T00:02:00.000+08:00|                   false|                        20.09|
|2017-11-01T00:03:00.000+08:00|                   false|                        20.18|
|2017-11-01T00:04:00.000+08:00|                   false|                        21.13|
|2017-11-01T00:05:00.000+08:00|                   false|                        22.72|
|2017-11-01T00:06:00.000+08:00|                   false|                        20.71|
|2017-11-01T00:07:00.000+08:00|                   false|                        21.45|
|2017-11-01T00:08:00.000+08:00|                   false|                        22.58|
|2017-11-01T00:09:00.000+08:00|                   false|                        20.98|
+-----------------------------+------------------------+-----------------------------+
Total line number = 10
It costs 0.000s
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><ul><li>Example 2: LIMIT clause with OFFSET</li></ul><p>The SQL statement is:</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> <span class="token keyword">status</span><span class="token punctuation">,</span> temperature <span class="token keyword">from</span> root<span class="token punctuation">.</span>ln<span class="token punctuation">.</span>wf01<span class="token punctuation">.</span>wt01 <span class="token keyword">limit</span> <span class="token number">5</span> <span class="token keyword">offset</span> <span class="token number">3</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>which means:</p><p>The selected device is ln group wf01 plant wt01 device; the selected timeseries is &quot;status&quot; and &quot;temperature&quot;. The SQL statement requires rows 3 to 7 of the query result be returned (with the first row numbered as row 0).</p><p>The result is shown below:</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>+-----------------------------+------------------------+-----------------------------+
|                         Time|root.ln.wf01.wt01.status|root.ln.wf01.wt01.temperature|
+-----------------------------+------------------------+-----------------------------+
|2017-11-01T00:03:00.000+08:00|                   false|                        20.18|
|2017-11-01T00:04:00.000+08:00|                   false|                        21.13|
|2017-11-01T00:05:00.000+08:00|                   false|                        22.72|
|2017-11-01T00:06:00.000+08:00|                   false|                        20.71|
|2017-11-01T00:07:00.000+08:00|                   false|                        21.45|
+-----------------------------+------------------------+-----------------------------+
Total line number = 5
It costs 0.342s
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><ul><li>Example 3: LIMIT clause combined with WHERE clause</li></ul><p>The SQL statement is:</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> <span class="token keyword">status</span><span class="token punctuation">,</span>temperature <span class="token keyword">from</span> root<span class="token punctuation">.</span>ln<span class="token punctuation">.</span>wf01<span class="token punctuation">.</span>wt01 <span class="token keyword">where</span> <span class="token keyword">time</span> <span class="token operator">&gt;</span> <span class="token number">2017</span><span class="token operator">-</span><span class="token number">11</span><span class="token operator">-</span><span class="token number">01</span>T00:<span class="token number">05</span>:<span class="token number">00.000</span> <span class="token operator">and</span> <span class="token keyword">time</span><span class="token operator">&lt;</span> <span class="token number">2017</span><span class="token operator">-</span><span class="token number">11</span><span class="token operator">-</span><span class="token number">01</span>T00:<span class="token number">12</span>:<span class="token number">00.000</span> <span class="token keyword">limit</span> <span class="token number">2</span> <span class="token keyword">offset</span> <span class="token number">3</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>which means:</p><p>The selected device is ln group wf01 plant wt01 device; the selected timeseries is &quot;status&quot; and &quot;temperature&quot;. The SQL statement requires rows 3 to 4 of the status and temperature sensor values between the time point of &quot;2017-11-01T00:05:00.000&quot; and &quot;2017-11-01T00:12:00.000&quot; (with the first row numbered as row 0).</p><p>The result is shown below:</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>+-----------------------------+------------------------+-----------------------------+
|                         Time|root.ln.wf01.wt01.status|root.ln.wf01.wt01.temperature|
+-----------------------------+------------------------+-----------------------------+
|2017-11-01T00:03:00.000+08:00|                   false|                        20.18|
|2017-11-01T00:04:00.000+08:00|                   false|                        21.13|
|2017-11-01T00:05:00.000+08:00|                   false|                        22.72|
|2017-11-01T00:06:00.000+08:00|                   false|                        20.71|
|2017-11-01T00:07:00.000+08:00|                   false|                        21.45|
+-----------------------------+------------------------+-----------------------------+
Total line number = 5
It costs 0.000s
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><ul><li>Example 4: LIMIT clause combined with GROUP BY clause</li></ul><p>The SQL statement is:</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> <span class="token function">count</span><span class="token punctuation">(</span><span class="token keyword">status</span><span class="token punctuation">)</span><span class="token punctuation">,</span> max_value<span class="token punctuation">(</span>temperature<span class="token punctuation">)</span> <span class="token keyword">from</span> root<span class="token punctuation">.</span>ln<span class="token punctuation">.</span>wf01<span class="token punctuation">.</span>wt01 <span class="token keyword">group</span> <span class="token keyword">by</span> <span class="token punctuation">(</span><span class="token punctuation">[</span><span class="token number">2017</span><span class="token operator">-</span><span class="token number">11</span><span class="token operator">-</span><span class="token number">01</span>T00:<span class="token number">00</span>:<span class="token number">00</span><span class="token punctuation">,</span> <span class="token number">2017</span><span class="token operator">-</span><span class="token number">11</span><span class="token operator">-</span><span class="token number">07</span>T23:<span class="token number">00</span>:<span class="token number">00</span><span class="token punctuation">)</span><span class="token punctuation">,</span><span class="token number">1</span>d<span class="token punctuation">)</span> <span class="token keyword">limit</span> <span class="token number">5</span> <span class="token keyword">offset</span> <span class="token number">3</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>which means:</p><p>The SQL statement clause requires rows 3 to 7 of the query result be returned (with the first row numbered as row 0).</p><p>The result is shown below:</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>+-----------------------------+-------------------------------+----------------------------------------+
|                         Time|count(root.ln.wf01.wt01.status)|max_value(root.ln.wf01.wt01.temperature)|
+-----------------------------+-------------------------------+----------------------------------------+
|2017-11-04T00:00:00.000+08:00|                           1440|                                    26.0|
|2017-11-05T00:00:00.000+08:00|                           1440|                                    26.0|
|2017-11-06T00:00:00.000+08:00|                           1440|                                   25.99|
|2017-11-07T00:00:00.000+08:00|                           1380|                                    26.0|
+-----------------------------+-------------------------------+----------------------------------------+
Total line number = 4
It costs 0.016s
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><h3 id="column-control-over-query-results" tabindex="-1"><a class="header-anchor" href="#column-control-over-query-results"><span>Column Control over Query Results</span></a></h3><p>By using SLIMIT and SOFFSET clauses, users can control the query results in a column-related manner. We will demonstrate how to use SLIMIT and SOFFSET clauses through the following examples.</p><ul><li>Example 1: basic SLIMIT clause</li></ul><p>The SQL statement is:</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> <span class="token operator">*</span> <span class="token keyword">from</span> root<span class="token punctuation">.</span>ln<span class="token punctuation">.</span>wf01<span class="token punctuation">.</span>wt01 <span class="token keyword">where</span> <span class="token keyword">time</span> <span class="token operator">&gt;</span> <span class="token number">2017</span><span class="token operator">-</span><span class="token number">11</span><span class="token operator">-</span><span class="token number">01</span>T00:<span class="token number">05</span>:<span class="token number">00.000</span> <span class="token operator">and</span> <span class="token keyword">time</span> <span class="token operator">&lt;</span> <span class="token number">2017</span><span class="token operator">-</span><span class="token number">11</span><span class="token operator">-</span><span class="token number">01</span>T00:<span class="token number">12</span>:<span class="token number">00.000</span> slimit <span class="token number">1</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>which means:</p><p>The selected device is ln group wf01 plant wt01 device; the selected timeseries is the first column under this device, i.e., the power supply status. The SQL statement requires the status sensor values between the time point of &quot;2017-11-01T00:05:00.000&quot; and &quot;2017-11-01T00:12:00.000&quot; be selected.</p><p>The result is shown below:</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>+-----------------------------+-----------------------------+
|                         Time|root.ln.wf01.wt01.temperature|
+-----------------------------+-----------------------------+
|2017-11-01T00:06:00.000+08:00|                        20.71|
|2017-11-01T00:07:00.000+08:00|                        21.45|
|2017-11-01T00:08:00.000+08:00|                        22.58|
|2017-11-01T00:09:00.000+08:00|                        20.98|
|2017-11-01T00:10:00.000+08:00|                        25.52|
|2017-11-01T00:11:00.000+08:00|                        22.91|
+-----------------------------+-----------------------------+
Total line number = 6
It costs 0.000s
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><ul><li>Example 2: SLIMIT clause with SOFFSET</li></ul><p>The SQL statement is:</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> <span class="token operator">*</span> <span class="token keyword">from</span> root<span class="token punctuation">.</span>ln<span class="token punctuation">.</span>wf01<span class="token punctuation">.</span>wt01 <span class="token keyword">where</span> <span class="token keyword">time</span> <span class="token operator">&gt;</span> <span class="token number">2017</span><span class="token operator">-</span><span class="token number">11</span><span class="token operator">-</span><span class="token number">01</span>T00:<span class="token number">05</span>:<span class="token number">00.000</span> <span class="token operator">and</span> <span class="token keyword">time</span> <span class="token operator">&lt;</span> <span class="token number">2017</span><span class="token operator">-</span><span class="token number">11</span><span class="token operator">-</span><span class="token number">01</span>T00:<span class="token number">12</span>:<span class="token number">00.000</span> slimit <span class="token number">1</span> soffset <span class="token number">1</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>which means:</p><p>The selected device is ln group wf01 plant wt01 device; the selected timeseries is the second column under this device, i.e., the temperature. The SQL statement requires the temperature sensor values between the time point of &quot;2017-11-01T00:05:00.000&quot; and &quot;2017-11-01T00:12:00.000&quot; be selected.</p><p>The result is shown below:</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>+-----------------------------+------------------------+
|                         Time|root.ln.wf01.wt01.status|
+-----------------------------+------------------------+
|2017-11-01T00:06:00.000+08:00|                   false|
|2017-11-01T00:07:00.000+08:00|                   false|
|2017-11-01T00:08:00.000+08:00|                   false|
|2017-11-01T00:09:00.000+08:00|                   false|
|2017-11-01T00:10:00.000+08:00|                    true|
|2017-11-01T00:11:00.000+08:00|                   false|
+-----------------------------+------------------------+
Total line number = 6
It costs 0.003s
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><ul><li>Example 3: SLIMIT clause combined with GROUP BY clause</li></ul><p>The SQL statement is:</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> max_value<span class="token punctuation">(</span><span class="token operator">*</span><span class="token punctuation">)</span> <span class="token keyword">from</span> root<span class="token punctuation">.</span>ln<span class="token punctuation">.</span>wf01<span class="token punctuation">.</span>wt01 <span class="token keyword">group</span> <span class="token keyword">by</span> <span class="token punctuation">(</span><span class="token punctuation">[</span><span class="token number">2017</span><span class="token operator">-</span><span class="token number">11</span><span class="token operator">-</span><span class="token number">01</span>T00:<span class="token number">00</span>:<span class="token number">00</span><span class="token punctuation">,</span> <span class="token number">2017</span><span class="token operator">-</span><span class="token number">11</span><span class="token operator">-</span><span class="token number">07</span>T23:<span class="token number">00</span>:<span class="token number">00</span><span class="token punctuation">)</span><span class="token punctuation">,</span><span class="token number">1</span>d<span class="token punctuation">)</span> slimit <span class="token number">1</span> soffset <span class="token number">1</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>The result is shown below:</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>+-----------------------------+-----------------------------------+
|                         Time|max_value(root.ln.wf01.wt01.status)|
+-----------------------------+-----------------------------------+
|2017-11-01T00:00:00.000+08:00|                               true|
|2017-11-02T00:00:00.000+08:00|                               true|
|2017-11-03T00:00:00.000+08:00|                               true|
|2017-11-04T00:00:00.000+08:00|                               true|
|2017-11-05T00:00:00.000+08:00|                               true|
|2017-11-06T00:00:00.000+08:00|                               true|
|2017-11-07T00:00:00.000+08:00|                               true|
+-----------------------------+-----------------------------------+
Total line number = 7
It costs 0.000s
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><h3 id="row-and-column-control-over-query-results" tabindex="-1"><a class="header-anchor" href="#row-and-column-control-over-query-results"><span>Row and Column Control over Query Results</span></a></h3><p>In addition to row or column control over query results, IoTDB allows users to control both rows and columns of query results. Here is a complete example with both LIMIT clauses and SLIMIT clauses.</p><p>The SQL statement is:</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> <span class="token operator">*</span> <span class="token keyword">from</span> root<span class="token punctuation">.</span>ln<span class="token punctuation">.</span>wf01<span class="token punctuation">.</span>wt01 <span class="token keyword">limit</span> <span class="token number">10</span> <span class="token keyword">offset</span> <span class="token number">100</span> slimit <span class="token number">2</span> soffset <span class="token number">0</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>which means:</p><p>The selected device is ln group wf01 plant wt01 device; the selected timeseries is columns 0 to 1 under this device (with the first column numbered as column 0). The SQL statement clause requires rows 100 to 109 of the query result be returned (with the first row numbered as row 0).</p><p>The result is shown below:</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>+-----------------------------+-----------------------------+------------------------+
|                         Time|root.ln.wf01.wt01.temperature|root.ln.wf01.wt01.status|
+-----------------------------+-----------------------------+------------------------+
|2017-11-01T01:40:00.000+08:00|                        21.19|                   false|
|2017-11-01T01:41:00.000+08:00|                        22.79|                   false|
|2017-11-01T01:42:00.000+08:00|                        22.98|                   false|
|2017-11-01T01:43:00.000+08:00|                        21.52|                   false|
|2017-11-01T01:44:00.000+08:00|                        23.45|                    true|
|2017-11-01T01:45:00.000+08:00|                        24.06|                    true|
|2017-11-01T01:46:00.000+08:00|                         22.6|                   false|
|2017-11-01T01:47:00.000+08:00|                        23.78|                    true|
|2017-11-01T01:48:00.000+08:00|                        24.72|                    true|
|2017-11-01T01:49:00.000+08:00|                        24.68|                    true|
+-----------------------------+-----------------------------+------------------------+
Total line number = 10
It costs 0.009s
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><h3 id="error-handling" tabindex="-1"><a class="header-anchor" href="#error-handling"><span>Error Handling</span></a></h3><p>If the parameter N/SN of LIMIT/SLIMIT exceeds the size of the result set, IoTDB returns all the results as expected. For example, the query result of the original SQL statement consists of six rows, and we select the first 100 rows through the LIMIT clause:</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> <span class="token keyword">status</span><span class="token punctuation">,</span>temperature <span class="token keyword">from</span> root<span class="token punctuation">.</span>ln<span class="token punctuation">.</span>wf01<span class="token punctuation">.</span>wt01 <span class="token keyword">where</span> <span class="token keyword">time</span> <span class="token operator">&gt;</span> <span class="token number">2017</span><span class="token operator">-</span><span class="token number">11</span><span class="token operator">-</span><span class="token number">01</span>T00:<span class="token number">05</span>:<span class="token number">00.000</span> <span class="token operator">and</span> <span class="token keyword">time</span> <span class="token operator">&lt;</span> <span class="token number">2017</span><span class="token operator">-</span><span class="token number">11</span><span class="token operator">-</span><span class="token number">01</span>T00:<span class="token number">12</span>:<span class="token number">00.000</span> <span class="token keyword">limit</span> <span class="token number">100</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>The result is shown below:</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>+-----------------------------+------------------------+-----------------------------+
|                         Time|root.ln.wf01.wt01.status|root.ln.wf01.wt01.temperature|
+-----------------------------+------------------------+-----------------------------+
|2017-11-01T00:06:00.000+08:00|                   false|                        20.71|
|2017-11-01T00:07:00.000+08:00|                   false|                        21.45|
|2017-11-01T00:08:00.000+08:00|                   false|                        22.58|
|2017-11-01T00:09:00.000+08:00|                   false|                        20.98|
|2017-11-01T00:10:00.000+08:00|                    true|                        25.52|
|2017-11-01T00:11:00.000+08:00|                   false|                        22.91|
+-----------------------------+------------------------+-----------------------------+
Total line number = 6
It costs 0.005s
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>If the parameter N/SN of LIMIT/SLIMIT clause exceeds the allowable maximum value (N/SN is of type int64), the system prompts errors. For example, executing the following SQL statement:</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> <span class="token keyword">status</span><span class="token punctuation">,</span>temperature <span class="token keyword">from</span> root<span class="token punctuation">.</span>ln<span class="token punctuation">.</span>wf01<span class="token punctuation">.</span>wt01 <span class="token keyword">where</span> <span class="token keyword">time</span> <span class="token operator">&gt;</span> <span class="token number">2017</span><span class="token operator">-</span><span class="token number">11</span><span class="token operator">-</span><span class="token number">01</span>T00:<span class="token number">05</span>:<span class="token number">00.000</span> <span class="token operator">and</span> <span class="token keyword">time</span> <span class="token operator">&lt;</span> <span class="token number">2017</span><span class="token operator">-</span><span class="token number">11</span><span class="token operator">-</span><span class="token number">01</span>T00:<span class="token number">12</span>:<span class="token number">00.000</span> <span class="token keyword">limit</span> <span class="token number">9223372036854775808</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>The SQL statement will not be executed and the corresponding error prompt is given as follows:</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>Msg: 416: Out of range. LIMIT &lt;N&gt;: N should be Int64.
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>If the parameter N/SN of LIMIT/SLIMIT clause is not a positive intege, the system prompts errors. For example, executing the following SQL statement:</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> <span class="token keyword">status</span><span class="token punctuation">,</span>temperature <span class="token keyword">from</span> root<span class="token punctuation">.</span>ln<span class="token punctuation">.</span>wf01<span class="token punctuation">.</span>wt01 <span class="token keyword">where</span> <span class="token keyword">time</span> <span class="token operator">&gt;</span> <span class="token number">2017</span><span class="token operator">-</span><span class="token number">11</span><span class="token operator">-</span><span class="token number">01</span>T00:<span class="token number">05</span>:<span class="token number">00.000</span> <span class="token operator">and</span> <span class="token keyword">time</span> <span class="token operator">&lt;</span> <span class="token number">2017</span><span class="token operator">-</span><span class="token number">11</span><span class="token operator">-</span><span class="token number">01</span>T00:<span class="token number">12</span>:<span class="token number">00.000</span> <span class="token keyword">limit</span> <span class="token number">13.1</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>The SQL statement will not be executed and the corresponding error prompt is given as follows:</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>Msg: 401: line 1:129 mismatched input &#39;.&#39; expecting {&lt;EOF&gt;, &#39;;&#39;}
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>If the parameter OFFSET of LIMIT clause exceeds the size of the result set, IoTDB will return an empty result set. For example, executing the following SQL statement:</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> <span class="token keyword">status</span><span class="token punctuation">,</span>temperature <span class="token keyword">from</span> root<span class="token punctuation">.</span>ln<span class="token punctuation">.</span>wf01<span class="token punctuation">.</span>wt01 <span class="token keyword">where</span> <span class="token keyword">time</span> <span class="token operator">&gt;</span> <span class="token number">2017</span><span class="token operator">-</span><span class="token number">11</span><span class="token operator">-</span><span class="token number">01</span>T00:<span class="token number">05</span>:<span class="token number">00.000</span> <span class="token operator">and</span> <span class="token keyword">time</span> <span class="token operator">&lt;</span> <span class="token number">2017</span><span class="token operator">-</span><span class="token number">11</span><span class="token operator">-</span><span class="token number">01</span>T00:<span class="token number">12</span>:<span class="token number">00.000</span> <span class="token keyword">limit</span> <span class="token number">2</span> <span class="token keyword">offset</span> <span class="token number">6</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>The result is shown below:</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>+----+------------------------+-----------------------------+
|Time|root.ln.wf01.wt01.status|root.ln.wf01.wt01.temperature|
+----+------------------------+-----------------------------+
+----+------------------------+-----------------------------+
Empty set.
It costs 0.005s
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>If the parameter SOFFSET of SLIMIT clause is not smaller than the number of available timeseries, the system prompts errors. For example, executing the following SQL statement:</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> <span class="token operator">*</span> <span class="token keyword">from</span> root<span class="token punctuation">.</span>ln<span class="token punctuation">.</span>wf01<span class="token punctuation">.</span>wt01 <span class="token keyword">where</span> <span class="token keyword">time</span> <span class="token operator">&gt;</span> <span class="token number">2017</span><span class="token operator">-</span><span class="token number">11</span><span class="token operator">-</span><span class="token number">01</span>T00:<span class="token number">05</span>:<span class="token number">00.000</span> <span class="token operator">and</span> <span class="token keyword">time</span> <span class="token operator">&lt;</span> <span class="token number">2017</span><span class="token operator">-</span><span class="token number">11</span><span class="token operator">-</span><span class="token number">01</span>T00:<span class="token number">12</span>:<span class="token number">00.000</span> slimit <span class="token number">1</span> soffset <span class="token number">2</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>The SQL statement will not be executed and the corresponding error prompt is given as follows:</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>Msg: 411: Meet error in query process: The value of SOFFSET (2) is equal to or exceeds the number of sequences (2) that can actually be returned.
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><h2 id="order-by-clause-1" tabindex="-1"><a class="header-anchor" href="#order-by-clause-1"><span><code>ORDER BY</code> CLAUSE</span></a></h2><h3 id="order-by-in-align-by-time-mode" tabindex="-1"><a class="header-anchor" href="#order-by-in-align-by-time-mode"><span>Order by in ALIGN BY TIME mode</span></a></h3><p>The result set of IoTDB is in ALIGN BY TIME mode by default and <code>ORDER BY TIME</code> clause can also be used to specify the ordering of timestamp. The SQL statement is:</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> <span class="token operator">*</span> <span class="token keyword">from</span> root<span class="token punctuation">.</span>ln<span class="token punctuation">.</span><span class="token operator">*</span><span class="token operator">*</span> <span class="token keyword">where</span> <span class="token keyword">time</span> <span class="token operator">&lt;=</span> <span class="token number">2017</span><span class="token operator">-</span><span class="token number">11</span><span class="token operator">-</span><span class="token number">01</span>T00:<span class="token number">01</span>:<span class="token number">00</span> <span class="token keyword">order</span> <span class="token keyword">by</span> <span class="token keyword">time</span> <span class="token keyword">desc</span><span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>Results：</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>+-----------------------------+--------------------------+------------------------+-----------------------------+------------------------+
|                         Time|root.ln.wf02.wt02.hardware|root.ln.wf02.wt02.status|root.ln.wf01.wt01.temperature|root.ln.wf01.wt01.status|
+-----------------------------+--------------------------+------------------------+-----------------------------+------------------------+
|2017-11-01T00:01:00.000+08:00|                        v2|                    true|                        24.36|                    true|
|2017-11-01T00:00:00.000+08:00|                        v2|                    true|                        25.96|                    true|
|1970-01-01T08:00:00.002+08:00|                        v2|                   false|                         null|                    null|
|1970-01-01T08:00:00.001+08:00|                        v1|                    true|                         null|                    null|
+-----------------------------+--------------------------+------------------------+-----------------------------+------------------------+
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><h3 id="order-by-in-align-by-device-mode" tabindex="-1"><a class="header-anchor" href="#order-by-in-align-by-device-mode"><span>Order by in ALIGN BY DEVICE mode</span></a></h3><p>When querying in ALIGN BY DEVICE mode, <code>ORDER BY</code> clause can be used to specify the ordering of result set.</p><p>ALIGN BY DEVICE mode supports four kinds of clauses with two sort keys which are <code>Device</code> and <code>Time</code>.</p><ol><li><p><code>ORDER BY DEVICE</code>: sort by the alphabetical order of the device name. The devices with the same column names will be clustered in a group view.</p></li><li><p><code>ORDER BY TIME</code>: sort by the timestamp, the data points from different devices will be shuffled according to the timestamp.</p></li><li><p><code>ORDER BY DEVICE,TIME</code>: sort by the alphabetical order of the device name. The data points with the same device name will be sorted by timestamp.</p></li><li><p><code>ORDER BY TIME,DEVICE</code>: sort by timestamp. The data points with the same time will be sorted by the alphabetical order of the device name.</p></li></ol><blockquote><p>To make the result set more legible, when <code>ORDER BY</code> clause is not used, default settings will be provided.<br> The default ordering clause is <code>ORDER BY DEVICE,TIME</code> and the default ordering is <code>ASC</code>.</p></blockquote><p>When <code>Device</code> is the main sort key, the result set is sorted by device name first, then by timestamp in the group with the same device name, the SQL statement is:</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> <span class="token operator">*</span> <span class="token keyword">from</span> root<span class="token punctuation">.</span>ln<span class="token punctuation">.</span><span class="token operator">*</span><span class="token operator">*</span> <span class="token keyword">where</span> <span class="token keyword">time</span> <span class="token operator">&lt;=</span> <span class="token number">2017</span><span class="token operator">-</span><span class="token number">11</span><span class="token operator">-</span><span class="token number">01</span>T00:<span class="token number">01</span>:<span class="token number">00</span> <span class="token keyword">order</span> <span class="token keyword">by</span> device <span class="token keyword">desc</span><span class="token punctuation">,</span><span class="token keyword">time</span> <span class="token keyword">asc</span> align <span class="token keyword">by</span> device<span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>The result shows below:</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>+-----------------------------+-----------------+--------+------+-----------+
|                         Time|           Device|hardware|status|temperature|
+-----------------------------+-----------------+--------+------+-----------+
|1970-01-01T08:00:00.001+08:00|root.ln.wf02.wt02|      v1|  true|       null|
|1970-01-01T08:00:00.002+08:00|root.ln.wf02.wt02|      v2| false|       null|
|2017-11-01T00:00:00.000+08:00|root.ln.wf02.wt02|      v2|  true|       null|
|2017-11-01T00:01:00.000+08:00|root.ln.wf02.wt02|      v2|  true|       null|
|2017-11-01T00:00:00.000+08:00|root.ln.wf01.wt01|    null|  true|      25.96|
|2017-11-01T00:01:00.000+08:00|root.ln.wf01.wt01|    null|  true|      24.36|
+-----------------------------+-----------------+--------+------+-----------+
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>When <code>Time</code> is the main sort key, the result set is sorted by timestamp first, then by device name in data points with the same timestamp. The SQL statement is:</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> <span class="token operator">*</span> <span class="token keyword">from</span> root<span class="token punctuation">.</span>ln<span class="token punctuation">.</span><span class="token operator">*</span><span class="token operator">*</span> <span class="token keyword">where</span> <span class="token keyword">time</span> <span class="token operator">&lt;=</span> <span class="token number">2017</span><span class="token operator">-</span><span class="token number">11</span><span class="token operator">-</span><span class="token number">01</span>T00:<span class="token number">01</span>:<span class="token number">00</span> <span class="token keyword">order</span> <span class="token keyword">by</span> <span class="token keyword">time</span> <span class="token keyword">asc</span><span class="token punctuation">,</span>device <span class="token keyword">desc</span> align <span class="token keyword">by</span> device<span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>The result shows below:</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>+-----------------------------+-----------------+--------+------+-----------+
|                         Time|           Device|hardware|status|temperature|
+-----------------------------+-----------------+--------+------+-----------+
|1970-01-01T08:00:00.001+08:00|root.ln.wf02.wt02|      v1|  true|       null|
|1970-01-01T08:00:00.002+08:00|root.ln.wf02.wt02|      v2| false|       null|
|2017-11-01T00:00:00.000+08:00|root.ln.wf02.wt02|      v2|  true|       null|
|2017-11-01T00:00:00.000+08:00|root.ln.wf01.wt01|    null|  true|      25.96|
|2017-11-01T00:01:00.000+08:00|root.ln.wf02.wt02|      v2|  true|       null|
|2017-11-01T00:01:00.000+08:00|root.ln.wf01.wt01|    null|  true|      24.36|
+-----------------------------+-----------------+--------+------+-----------+
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>When <code>ORDER BY</code> clause is not used, sort in default way, the SQL statement is：</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> <span class="token operator">*</span> <span class="token keyword">from</span> root<span class="token punctuation">.</span>ln<span class="token punctuation">.</span><span class="token operator">*</span><span class="token operator">*</span> <span class="token keyword">where</span> <span class="token keyword">time</span> <span class="token operator">&lt;=</span> <span class="token number">2017</span><span class="token operator">-</span><span class="token number">11</span><span class="token operator">-</span><span class="token number">01</span>T00:<span class="token number">01</span>:<span class="token number">00</span> align <span class="token keyword">by</span> device<span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>The result below indicates <code>ORDER BY DEVICE ASC,TIME ASC</code> is the clause in default situation.<br><code>ASC</code> can be omitted because it&#39;s the default ordering.</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>+-----------------------------+-----------------+--------+------+-----------+
|                         Time|           Device|hardware|status|temperature|
+-----------------------------+-----------------+--------+------+-----------+
|2017-11-01T00:00:00.000+08:00|root.ln.wf01.wt01|    null|  true|      25.96|
|2017-11-01T00:01:00.000+08:00|root.ln.wf01.wt01|    null|  true|      24.36|
|1970-01-01T08:00:00.001+08:00|root.ln.wf02.wt02|      v1|  true|       null|
|1970-01-01T08:00:00.002+08:00|root.ln.wf02.wt02|      v2| false|       null|
|2017-11-01T00:00:00.000+08:00|root.ln.wf02.wt02|      v2|  true|       null|
|2017-11-01T00:01:00.000+08:00|root.ln.wf02.wt02|      v2|  true|       null|
+-----------------------------+-----------------+--------+------+-----------+
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>Besides，<code>ALIGN BY DEVICE</code> and <code>ORDER BY</code> clauses can be used with aggregate query，the SQL statement is：</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> <span class="token function">count</span><span class="token punctuation">(</span><span class="token operator">*</span><span class="token punctuation">)</span> <span class="token keyword">from</span> root<span class="token punctuation">.</span>ln<span class="token punctuation">.</span><span class="token operator">*</span><span class="token operator">*</span> <span class="token keyword">group</span> <span class="token keyword">by</span> <span class="token punctuation">(</span><span class="token punctuation">(</span><span class="token number">2017</span><span class="token operator">-</span><span class="token number">11</span><span class="token operator">-</span><span class="token number">01</span>T00:<span class="token number">00</span>:<span class="token number">00.000</span><span class="token operator">+</span><span class="token number">08</span>:<span class="token number">00</span><span class="token punctuation">,</span><span class="token number">2017</span><span class="token operator">-</span><span class="token number">11</span><span class="token operator">-</span><span class="token number">01</span>T00:<span class="token number">03</span>:<span class="token number">00.000</span><span class="token operator">+</span><span class="token number">08</span>:<span class="token number">00</span><span class="token punctuation">]</span><span class="token punctuation">,</span><span class="token number">1</span>m<span class="token punctuation">)</span> <span class="token keyword">order</span> <span class="token keyword">by</span> device <span class="token keyword">asc</span><span class="token punctuation">,</span><span class="token keyword">time</span> <span class="token keyword">asc</span> align <span class="token keyword">by</span> device
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>The result shows below:</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>+-----------------------------+-----------------+---------------+-------------+------------------+
|                         Time|           Device|count(hardware)|count(status)|count(temperature)|
+-----------------------------+-----------------+---------------+-------------+------------------+
|2017-11-01T00:01:00.000+08:00|root.ln.wf01.wt01|           null|            1|                 1|
|2017-11-01T00:02:00.000+08:00|root.ln.wf01.wt01|           null|            0|                 0|
|2017-11-01T00:03:00.000+08:00|root.ln.wf01.wt01|           null|            0|                 0|
|2017-11-01T00:01:00.000+08:00|root.ln.wf02.wt02|              1|            1|              null|
|2017-11-01T00:02:00.000+08:00|root.ln.wf02.wt02|              0|            0|              null|
|2017-11-01T00:03:00.000+08:00|root.ln.wf02.wt02|              0|            0|              null|
+-----------------------------+-----------------+---------------+-------------+------------------+
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><h3 id="order-by-arbitrary-expressions" tabindex="-1"><a class="header-anchor" href="#order-by-arbitrary-expressions"><span>Order by arbitrary expressions</span></a></h3><p>In addition to the predefined keywords &quot;Time&quot; and &quot;Device&quot; in IoTDB, <code>ORDER BY</code> can also be used to sort by any expressions.</p><p>When sorting, <code>ASC</code> or <code>DESC</code> can be used to specify the sorting order, and <code>NULLS</code> syntax is supported to specify the priority of NULL values in the sorting. By default, <code>NULLS FIRST</code> places NULL values at the top of the result, and <code>NULLS LAST</code> ensures that NULL values appear at the end of the result. If not specified in the clause, the default order is ASC with NULLS LAST.</p><p>Here are several examples of queries for sorting arbitrary expressions using the following data:</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>+-----------------------------+-------------+-------+-------+--------+-------+
|                         Time|       Device|   base|  score|   bonus|  total|    
+-----------------------------+-------------+-------+-------+--------+-------+
|1970-01-01T08:00:00.000+08:00|     root.one|     12|   50.0|    45.0|  107.0|  
|1970-01-02T08:00:00.000+08:00|     root.one|     10|   50.0|    45.0|  105.0|
|1970-01-03T08:00:00.000+08:00|     root.one|      8|   50.0|    45.0|  103.0|       
|1970-01-01T08:00:00.010+08:00|     root.two|      9|   50.0|    15.0|   74.0|   
|1970-01-01T08:00:00.020+08:00|     root.two|      8|   10.0|    15.0|   33.0|  
|1970-01-01T08:00:00.010+08:00|   root.three|      9|   null|    24.0|   33.0|    
|1970-01-01T08:00:00.020+08:00|   root.three|      8|   null|    22.5|   30.5|   
|1970-01-01T08:00:00.030+08:00|   root.three|      7|   null|    23.5|   30.5|   
|1970-01-01T08:00:00.010+08:00|    root.four|      9|   32.0|    45.0|   86.0|  
|1970-01-01T08:00:00.020+08:00|    root.four|      8|   32.0|    45.0|   85.0|   
|1970-01-01T08:00:00.030+08:00|    root.five|      7|   53.0|    44.0|  104.0|
|1970-01-01T08:00:00.040+08:00|    root.five|      6|   54.0|    42.0|  102.0|     
+-----------------------------+-------------+-------+-------+--------+-------+
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>When you need to sort the results based on the base score score, you can use the following SQL:</p><div class="language-Sql line-numbers-mode" data-ext="Sql" data-title="Sql"><pre class="language-Sql"><code>select score from root.** order by score desc align by device
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>This will give you the following results:</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>+-----------------------------+---------+-----+
|                         Time|   Device|score|
+-----------------------------+---------+-----+
|1970-01-01T08:00:00.040+08:00|root.five| 54.0|
|1970-01-01T08:00:00.030+08:00|root.five| 53.0|
|1970-01-01T08:00:00.000+08:00| root.one| 50.0|
|1970-01-02T08:00:00.000+08:00| root.one| 50.0|
|1970-01-03T08:00:00.000+08:00| root.one| 50.0|
|1970-01-01T08:00:00.000+08:00| root.two| 50.0|
|1970-01-01T08:00:00.010+08:00| root.two| 50.0|
|1970-01-01T08:00:00.010+08:00|root.four| 32.0|
|1970-01-01T08:00:00.020+08:00|root.four| 32.0|
|1970-01-01T08:00:00.020+08:00| root.two| 10.0|
+-----------------------------+---------+-----+
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>If you want to sort the results based on the total score, you can use an expression in the <code>ORDER BY</code> clause to perform the calculation:</p><div class="language-Sql line-numbers-mode" data-ext="Sql" data-title="Sql"><pre class="language-Sql"><code>select score,total from root.one order by base+score+bonus desc
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>This SQL is equivalent to:</p><div class="language-Sql line-numbers-mode" data-ext="Sql" data-title="Sql"><pre class="language-Sql"><code>select score,total from root.one order by total desc
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>Here are the results:</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>+-----------------------------+--------------+--------------+
|                         Time|root.one.score|root.one.total|
+-----------------------------+--------------+--------------+
|1970-01-01T08:00:00.000+08:00|          50.0|         107.0|
|1970-01-02T08:00:00.000+08:00|          50.0|         105.0|
|1970-01-03T08:00:00.000+08:00|          50.0|         103.0|
+-----------------------------+--------------+--------------+
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>If you want to sort the results based on the total score and, in case of tied scores, sort by score, base, bonus, and submission time in descending order, you can specify multiple layers of sorting using multiple expressions:</p><div class="language-Sql line-numbers-mode" data-ext="Sql" data-title="Sql"><pre class="language-Sql"><code>select base, score, bonus, total from root.** order by total desc NULLS Last,
                                  score desc NULLS Last,
                                  bonus desc NULLS Last,
                                  time desc align by device
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>Here are the results:</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>+-----------------------------+----------+----+-----+-----+-----+
|                         Time|    Device|base|score|bonus|total|
+-----------------------------+----------+----+-----+-----+-----+
|1970-01-01T08:00:00.000+08:00|  root.one|  12| 50.0| 45.0|107.0|
|1970-01-02T08:00:00.000+08:00|  root.one|  10| 50.0| 45.0|105.0|
|1970-01-01T08:00:00.030+08:00| root.five|   7| 53.0| 44.0|104.0|
|1970-01-03T08:00:00.000+08:00|  root.one|   8| 50.0| 45.0|103.0|
|1970-01-01T08:00:00.040+08:00| root.five|   6| 54.0| 42.0|102.0|
|1970-01-01T08:00:00.010+08:00| root.four|   9| 32.0| 45.0| 86.0|
|1970-01-01T08:00:00.020+08:00| root.four|   8| 32.0| 45.0| 85.0|
|1970-01-01T08:00:00.010+08:00|  root.two|   9| 50.0| 15.0| 74.0|
|1970-01-01T08:00:00.000+08:00|  root.two|   9| 50.0| 15.0| 74.0|
|1970-01-01T08:00:00.020+08:00|  root.two|   8| 10.0| 15.0| 33.0|
|1970-01-01T08:00:00.010+08:00|root.three|   9| null| 24.0| 33.0|
|1970-01-01T08:00:00.030+08:00|root.three|   7| null| 23.5| 30.5|
|1970-01-01T08:00:00.020+08:00|root.three|   8| null| 22.5| 30.5|
+-----------------------------+----------+----+-----+-----+-----+
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>In the <code>ORDER BY</code> clause, you can also use aggregate query expressions. For example:</p><div class="language-Sql line-numbers-mode" data-ext="Sql" data-title="Sql"><pre class="language-Sql"><code>select min_value(total) from root.** order by min_value(total) asc align by device
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>This will give you the following results:</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>+----------+----------------+
|    Device|min_value(total)|
+----------+----------------+
|root.three|            30.5|
|  root.two|            33.0|
| root.four|            85.0|
| root.five|           102.0|
|  root.one|           103.0|
+----------+----------------+
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>When specifying multiple columns in the query, the unsorted columns will change order along with the rows and sorted columns. The order of rows when the sorting columns are the same may vary depending on the specific implementation (no fixed order). For example:</p><div class="language-Sql line-numbers-mode" data-ext="Sql" data-title="Sql"><pre class="language-Sql"><code>select min_value(total),max_value(base) from root.** order by max_value(total) desc align by device
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>This will give you the following results:<br> ·</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>+----------+----------------+---------------+
|    Device|min_value(total)|max_value(base)|
+----------+----------------+---------------+
|  root.one|           103.0|             12|
| root.five|           102.0|              7|
| root.four|            85.0|              9|
|  root.two|            33.0|              9|
|root.three|            30.5|              9|
+----------+----------------+---------------+
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>You can use both <code>ORDER BY DEVICE,TIME</code> and <code>ORDER BY EXPRESSION</code> together. For example:</p><div class="language-Sql line-numbers-mode" data-ext="Sql" data-title="Sql"><pre class="language-Sql"><code>select score from root.** order by device asc, score desc, time asc align by device
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>This will give you the following results:</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>+-----------------------------+---------+-----+
|                         Time|   Device|score|
+-----------------------------+---------+-----+
|1970-01-01T08:00:00.040+08:00|root.five| 54.0|
|1970-01-01T08:00:00.030+08:00|root.five| 53.0|
|1970-01-01T08:00:00.010+08:00|root.four| 32.0|
|1970-01-01T08:00:00.020+08:00|root.four| 32.0|
|1970-01-01T08:00:00.000+08:00| root.one| 50.0|
|1970-01-02T08:00:00.000+08:00| root.one| 50.0|
|1970-01-03T08:00:00.000+08:00| root.one| 50.0|
|1970-01-01T08:00:00.000+08:00| root.two| 50.0|
|1970-01-01T08:00:00.010+08:00| root.two| 50.0|
|1970-01-01T08:00:00.020+08:00| root.two| 10.0|
+-----------------------------+---------+-----+
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><h2 id="align-by-clause-1" tabindex="-1"><a class="header-anchor" href="#align-by-clause-1"><span><code>ALIGN BY</code> CLAUSE</span></a></h2><p>In addition, IoTDB supports another result set format: <code>ALIGN BY DEVICE</code>.</p><h3 id="align-by-device" tabindex="-1"><a class="header-anchor" href="#align-by-device"><span>Align by Device</span></a></h3><p>The <code>ALIGN BY DEVICE</code> indicates that the deviceId is considered as a column. Therefore, there are totally limited columns in the dataset.</p><blockquote><p>NOTE：</p><p>1.You can see the result of &#39;align by device&#39; as one relational table, <code>Time + Device</code> is the primary key of this Table.</p><p>2.The result is order by <code>Device</code> firstly, and then by <code>Time</code> order.</p></blockquote><p>The SQL statement is:</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> <span class="token operator">*</span> <span class="token keyword">from</span> root<span class="token punctuation">.</span>ln<span class="token punctuation">.</span><span class="token operator">*</span><span class="token operator">*</span> <span class="token keyword">where</span> <span class="token keyword">time</span> <span class="token operator">&lt;=</span> <span class="token number">2017</span><span class="token operator">-</span><span class="token number">11</span><span class="token operator">-</span><span class="token number">01</span>T00:<span class="token number">01</span>:<span class="token number">00</span> align <span class="token keyword">by</span> device<span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>The result shows below:</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>+-----------------------------+-----------------+-----------+------+--------+
|                         Time|           Device|temperature|status|hardware|
+-----------------------------+-----------------+-----------+------+--------+
|2017-11-01T00:00:00.000+08:00|root.ln.wf01.wt01|      25.96|  true|    null|
|2017-11-01T00:01:00.000+08:00|root.ln.wf01.wt01|      24.36|  true|    null|
|1970-01-01T08:00:00.001+08:00|root.ln.wf02.wt02|       null|  true|      v1|
|1970-01-01T08:00:00.002+08:00|root.ln.wf02.wt02|       null| false|      v2|
|2017-11-01T00:00:00.000+08:00|root.ln.wf02.wt02|       null|  true|      v2|
|2017-11-01T00:01:00.000+08:00|root.ln.wf02.wt02|       null|  true|      v2|
+-----------------------------+-----------------+-----------+------+--------+
Total line number = 6
It costs 0.012s
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><h3 id="ordering-in-align-by-device" tabindex="-1"><a class="header-anchor" href="#ordering-in-align-by-device"><span>Ordering in ALIGN BY DEVICE</span></a></h3><p>ALIGN BY DEVICE mode arranges according to the device first, and sort each device in ascending order according to the timestamp. The ordering and priority can be adjusted through <code>ORDER BY</code> clause.</p><h2 id="into-clause-query-write-back" tabindex="-1"><a class="header-anchor" href="#into-clause-query-write-back"><span><code>INTO</code> CLAUSE (QUERY WRITE-BACK)</span></a></h2><p>The <code>SELECT INTO</code> statement copies data from query result set into target time series.</p><p>The application scenarios are as follows:</p><ul><li><strong>Implement IoTDB internal ETL</strong>: ETL the original data and write a new time series.</li><li><strong>Query result storage</strong>: Persistently store the query results, which acts like a materialized view.</li><li><strong>Non-aligned time series to aligned time series</strong>: Rewrite non-aligned time series into another aligned time series.</li></ul><h3 id="sql-syntax" tabindex="-1"><a class="header-anchor" href="#sql-syntax"><span>SQL Syntax</span></a></h3><h4 id="syntax-definition-2" tabindex="-1"><a class="header-anchor" href="#syntax-definition-2"><span>Syntax Definition</span></a></h4><p><strong>The following is the syntax definition of the <code>select</code> statement:</strong></p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code>selectIntoStatement
: <span class="token keyword">SELECT</span>
      resultColumn <span class="token punctuation">[</span><span class="token punctuation">,</span> resultColumn<span class="token punctuation">]</span> <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>
        <span class="token keyword">INTO</span> intoItem <span class="token punctuation">[</span><span class="token punctuation">,</span> intoItem<span class="token punctuation">]</span> <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>
        <span class="token keyword">FROM</span> prefixPath <span class="token punctuation">[</span><span class="token punctuation">,</span> prefixPath<span class="token punctuation">]</span> <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>
        <span class="token punctuation">[</span><span class="token keyword">WHERE</span> whereCondition<span class="token punctuation">]</span>
      <span class="token punctuation">[</span><span class="token keyword">GROUP</span> <span class="token keyword">BY</span> groupByTimeClause<span class="token punctuation">,</span> groupByLevelClause<span class="token punctuation">]</span>
      <span class="token punctuation">[</span>FILL {PREVIOUS <span class="token operator">|</span> LINEAR <span class="token operator">|</span> constant}<span class="token punctuation">]</span>
      <span class="token punctuation">[</span><span class="token keyword">LIMIT</span> rowLimit <span class="token keyword">OFFSET</span> rowOffset<span class="token punctuation">]</span>
      <span class="token punctuation">[</span>ALIGN <span class="token keyword">BY</span> DEVICE<span class="token punctuation">]</span>
<span class="token punctuation">;</span>

intoItem
: <span class="token punctuation">[</span>ALIGNED<span class="token punctuation">]</span> intoDevicePath <span class="token string">&#39;(&#39;</span> intoMeasurementName <span class="token punctuation">[</span><span class="token string">&#39;,&#39;</span> intoMeasurementName<span class="token punctuation">]</span><span class="token operator">*</span> <span class="token string">&#39;)&#39;</span>
    <span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><h4 id="into-clause-1" tabindex="-1"><a class="header-anchor" href="#into-clause-1"><span><code>INTO</code> Clause</span></a></h4><p>The <code>INTO</code> clause consists of several <code>intoItem</code>.</p><p>Each <code>intoItem</code> consists of a target device and a list of target measurements (similar to the <code>INTO</code> clause in an <code>INSERT</code> statement).</p><p>Each target measurement and device form a target time series, and an <code>intoItem</code> contains a series of time series. For example: <code>root.sg_copy.d1(s1, s2)</code> specifies two target time series <code>root.sg_copy.d1.s1</code> and <code>root.sg_copy.d1.s2</code>.</p><p>The target time series specified by the <code>INTO</code> clause must correspond one-to-one with the columns of the query result set. The specific rules are as follows:</p><ul><li><strong>Align by time</strong> (default): The number of target time series contained in all <code>intoItem</code> must be consistent with the number of columns in the query result set (except the time column) and correspond one-to-one in the order from left to right in the header.</li><li><strong>Align by device</strong> (using <code>ALIGN BY DEVICE</code>): the number of target devices specified in all <code>intoItem</code> is the same as the number of devices queried (i.e., the number of devices matched by the path pattern in the <code>FROM</code> clause), and One-to-one correspondence according to the output order of the result set device.<br><br>The number of measurements specified for each target device should be consistent with the number of columns in the query result set (except for the time and device columns). It should be in one-to-one correspondence from left to right in the header.</li></ul><p>For examples:</p><ul><li><strong>Example 1</strong> (aligned by time)</li></ul><div class="language-bash line-numbers-mode" data-ext="sh" data-title="sh"><pre class="language-bash"><code>IoTDB<span class="token operator">&gt;</span> <span class="token keyword">select</span> s1, s2 into root.sg_copy.d1<span class="token punctuation">(</span>t1<span class="token punctuation">)</span>, root.sg_copy.d2<span class="token punctuation">(</span>t1, t2<span class="token punctuation">)</span>, root.sg_copy.d1<span class="token punctuation">(</span>t2<span class="token punctuation">)</span> from root.sg.d1, root.sg.d2<span class="token punctuation">;</span>
+--------------+-------------------+--------+
<span class="token operator">|</span> <span class="token builtin class-name">source</span> <span class="token function">column</span><span class="token operator">|</span>  target timeseries<span class="token operator">|</span> written<span class="token operator">|</span>
+--------------+-------------------+--------+
<span class="token operator">|</span> root.sg.d1.s1<span class="token operator">|</span> root.sg_copy.d1.t1<span class="token operator">|</span>    <span class="token number">8000</span><span class="token operator">|</span>
+--------------+-------------------+--------+
<span class="token operator">|</span> root.sg.d2.s1<span class="token operator">|</span> root.sg_copy.d2.t1<span class="token operator">|</span>   <span class="token number">10000</span><span class="token operator">|</span>
+--------------+-------------------+--------+
<span class="token operator">|</span> root.sg.d1.s2<span class="token operator">|</span> root.sg_copy.d2.t2<span class="token operator">|</span>   <span class="token number">12000</span><span class="token operator">|</span>
+--------------+-------------------+--------+
<span class="token operator">|</span> root.sg.d2.s2<span class="token operator">|</span> root.sg_copy.d1.t2<span class="token operator">|</span>   <span class="token number">10000</span><span class="token operator">|</span>
+--------------+-------------------+--------+
Total line number <span class="token operator">=</span> <span class="token number">4</span>
It costs <span class="token number">0</span>.725s
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>This statement writes the query results of the four time series under the <code>root.sg</code> database to the four specified time series under the <code>root.sg_copy</code> database. Note that <code>root.sg_copy.d2(t1, t2)</code> can also be written as <code>root.sg_copy.d2(t1), root.sg_copy.d2(t2)</code>.</p><p>We can see that the writing of the <code>INTO</code> clause is very flexible as long as the combined target time series is not repeated and corresponds to the query result column one-to-one.</p><blockquote><p>In the result set displayed by <code>CLI</code>, the meaning of each column is as follows:</p><ul><li>The <code>source column</code> column represents the column name of the query result.</li><li><code>target timeseries</code> represents the target time series for the corresponding column to write.</li><li><code>written</code> indicates the amount of data expected to be written.</li></ul></blockquote><ul><li><strong>Example 2</strong> (aligned by time)</li></ul><div class="language-bash line-numbers-mode" data-ext="sh" data-title="sh"><pre class="language-bash"><code>IoTDB<span class="token operator">&gt;</span> <span class="token keyword">select</span> count<span class="token punctuation">(</span>s1 + s2<span class="token punctuation">)</span>, last_value<span class="token punctuation">(</span>s2<span class="token punctuation">)</span> into root.agg.count<span class="token punctuation">(</span>s1_add_s2<span class="token punctuation">)</span>, root.agg.last_value<span class="token punctuation">(</span>s2<span class="token punctuation">)</span> from root.sg.d1 group by <span class="token punctuation">(</span><span class="token punctuation">[</span><span class="token number">0</span>, <span class="token number">100</span><span class="token punctuation">)</span>, 10ms<span class="token punctuation">)</span><span class="token punctuation">;</span>
+--------------------------------------+-------------------------+--------+
<span class="token operator">|</span>                         <span class="token builtin class-name">source</span> <span class="token function">column</span><span class="token operator">|</span>        target timeseries<span class="token operator">|</span> written<span class="token operator">|</span>
+--------------------------------------+-------------------------+--------+
<span class="token operator">|</span>  count<span class="token punctuation">(</span>root.sg.d1.s1 + root.sg.d1.s2<span class="token punctuation">)</span><span class="token operator">|</span> root.agg.count.s1_add_s2<span class="token operator">|</span>      <span class="token number">10</span><span class="token operator">|</span>
+--------------------------------------+-------------------------+--------+
<span class="token operator">|</span>             last_value<span class="token punctuation">(</span>root.sg.d1.s2<span class="token punctuation">)</span><span class="token operator">|</span>   root.agg.last_value.s2<span class="token operator">|</span>      <span class="token number">10</span><span class="token operator">|</span>
+--------------------------------------+-------------------------+--------+
Total line number <span class="token operator">=</span> <span class="token number">2</span>
It costs <span class="token number">0</span>.375s
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>This statement stores the results of an aggregated query into the specified time series.</p><ul><li><strong>Example 3</strong> (aligned by device)</li></ul><div class="language-bash line-numbers-mode" data-ext="sh" data-title="sh"><pre class="language-bash"><code>IoTDB<span class="token operator">&gt;</span> <span class="token keyword">select</span> s1, s2 into root.sg_copy.d1<span class="token punctuation">(</span>t1, t2<span class="token punctuation">)</span>, root.sg_copy.d2<span class="token punctuation">(</span>t1, t2<span class="token punctuation">)</span> from root.sg.d1, root.sg.d2 align by device<span class="token punctuation">;</span>
+--------------+--------------+-------------------+--------+
<span class="token operator">|</span> <span class="token builtin class-name">source</span> device<span class="token operator">|</span> <span class="token builtin class-name">source</span> <span class="token function">column</span><span class="token operator">|</span>  target timeseries<span class="token operator">|</span> written<span class="token operator">|</span>
+--------------+--------------+-------------------+--------+
<span class="token operator">|</span>    root.sg.d1<span class="token operator">|</span>            s1<span class="token operator">|</span> root.sg_copy.d1.t1<span class="token operator">|</span>    <span class="token number">8000</span><span class="token operator">|</span>
+--------------+--------------+-------------------+--------+
<span class="token operator">|</span>    root.sg.d1<span class="token operator">|</span>            s2<span class="token operator">|</span> root.sg_copy.d1.t2<span class="token operator">|</span>   <span class="token number">11000</span><span class="token operator">|</span>
+--------------+--------------+-------------------+--------+
<span class="token operator">|</span>    root.sg.d2<span class="token operator">|</span>            s1<span class="token operator">|</span> root.sg_copy.d2.t1<span class="token operator">|</span>   <span class="token number">12000</span><span class="token operator">|</span>
+--------------+--------------+-------------------+--------+
<span class="token operator">|</span>    root.sg.d2<span class="token operator">|</span>            s2<span class="token operator">|</span> root.sg_copy.d2.t2<span class="token operator">|</span>    <span class="token number">9000</span><span class="token operator">|</span>
+--------------+--------------+-------------------+--------+
Total line number <span class="token operator">=</span> <span class="token number">4</span>
It costs <span class="token number">0</span>.625s
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>This statement also writes the query results of the four time series under the <code>root.sg</code> database to the four specified time series under the <code>root.sg_copy</code> database. However, in ALIGN BY DEVICE, the number of <code>intoItem</code> must be the same as the number of queried devices, and each queried device corresponds to one <code>intoItem</code>.</p><blockquote><p>When aligning the query by device, the result set displayed by <code>CLI</code> has one more column, the <code>source device</code> column indicating the queried device.</p></blockquote><ul><li><strong>Example 4</strong> (aligned by device)</li></ul><div class="language-bash line-numbers-mode" data-ext="sh" data-title="sh"><pre class="language-bash"><code>IoTDB<span class="token operator">&gt;</span> <span class="token keyword">select</span> s1 + s2 into root.expr.add<span class="token punctuation">(</span>d1s1_d1s2<span class="token punctuation">)</span>, root.expr.add<span class="token punctuation">(</span>d2s1_d2s2<span class="token punctuation">)</span> from root.sg.d1, root.sg.d2 align by device<span class="token punctuation">;</span>
+--------------+--------------+------------------------+--------+
<span class="token operator">|</span> <span class="token builtin class-name">source</span> device<span class="token operator">|</span> <span class="token builtin class-name">source</span> <span class="token function">column</span><span class="token operator">|</span>       target timeseries<span class="token operator">|</span> written<span class="token operator">|</span>
+--------------+--------------+------------------------+--------+
<span class="token operator">|</span>    root.sg.d1<span class="token operator">|</span>       s1 + s2<span class="token operator">|</span> root.expr.add.d1s1_d1s2<span class="token operator">|</span>   <span class="token number">10000</span><span class="token operator">|</span>
+--------------+--------------+------------------------+--------+
<span class="token operator">|</span>    root.sg.d2<span class="token operator">|</span>       s1 + s2<span class="token operator">|</span> root.expr.add.d2s1_d2s2<span class="token operator">|</span>   <span class="token number">10000</span><span class="token operator">|</span>
+--------------+--------------+------------------------+--------+
Total line number <span class="token operator">=</span> <span class="token number">2</span>
It costs <span class="token number">0</span>.532s
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>This statement stores the result of evaluating an expression into the specified time series.</p><h4 id="using-variable-placeholders" tabindex="-1"><a class="header-anchor" href="#using-variable-placeholders"><span>Using variable placeholders</span></a></h4><p>In particular, We can use variable placeholders to describe the correspondence between the target and query time series, simplifying the statement. The following two variable placeholders are currently supported:</p><ul><li>Suffix duplication character <code>::</code>: Copy the suffix (or measurement) of the query device, indicating that from this layer to the last layer (or measurement) of the device, the node name (or measurement) of the target device corresponds to the queried device The node name (or measurement) is the same.</li><li>Single-level node matcher <code>${i}</code>: Indicates that the current level node name of the target sequence is the same as the i-th level node name of the query sequence. For example, for the path <code>root.sg1.d1.s1</code>, <code>${1}</code> means <code>sg1</code>, <code>${2}</code> means <code>d1</code>, and <code>${3}</code> means <code>s1</code>.</li></ul><p>When using variable placeholders, there must be no ambiguity in the correspondence between <code>intoItem</code> and the columns of the query result set. The specific cases are classified as follows:</p><h5 id="align-by-time-default" tabindex="-1"><a class="header-anchor" href="#align-by-time-default"><span>ALIGN BY TIME (default)</span></a></h5><blockquote><p>Note: The variable placeholder <strong>can only describe the correspondence between time series</strong>. If the query includes aggregation and expression calculation, the columns in the query result cannot correspond to a time series, so neither the target device nor the measurement can use variable placeholders.</p></blockquote><h6 id="_1-the-target-device-does-not-use-variable-placeholders-the-target-measurement-list-uses-variable-placeholders" tabindex="-1"><a class="header-anchor" href="#_1-the-target-device-does-not-use-variable-placeholders-the-target-measurement-list-uses-variable-placeholders"><span>(1) The target device does not use variable placeholders &amp; the target measurement list uses variable placeholders</span></a></h6><p><strong>Limitations:</strong></p><ol><li>In each <code>intoItem</code>, the length of the list of physical quantities must be 1. <br> (If the length can be greater than 1, e.g. <code>root.sg1.d1(::, s1)</code>, it is not possible to determine which columns match <code>::</code>)</li><li>The number of <code>intoItem</code> is 1, or the same as the number of columns in the query result set. <br>(When the length of each target measurement list is 1, if there is only one <code>intoItem</code>, it means that all the query sequences are written to the same device; if the number of <code>intoItem</code> is consistent with the query sequence, it is expressed as each query time series specifies a target device; if <code>intoItem</code> is greater than one and less than the number of query sequences, it cannot be a one-to-one correspondence with the query sequence)</li></ol><p><strong>Matching method:</strong> Each query time series specifies the target device, and the target measurement is generated from the variable placeholder.</p><p><strong>Example:</strong></p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> s1<span class="token punctuation">,</span> s2
<span class="token keyword">into</span> root<span class="token punctuation">.</span>sg_copy<span class="token punctuation">.</span>d1<span class="token punctuation">(</span>::<span class="token punctuation">)</span><span class="token punctuation">,</span> root<span class="token punctuation">.</span>sg_copy<span class="token punctuation">.</span>d2<span class="token punctuation">(</span>s1<span class="token punctuation">)</span><span class="token punctuation">,</span> root<span class="token punctuation">.</span>sg_copy<span class="token punctuation">.</span>d1<span class="token punctuation">(</span>${<span class="token number">3</span>}<span class="token punctuation">)</span><span class="token punctuation">,</span> root<span class="token punctuation">.</span>sg_copy<span class="token punctuation">.</span>d2<span class="token punctuation">(</span>::<span class="token punctuation">)</span>
<span class="token keyword">from</span> root<span class="token punctuation">.</span>sg<span class="token punctuation">.</span>d1<span class="token punctuation">,</span> root<span class="token punctuation">.</span>sg<span class="token punctuation">.</span>d2<span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>This statement is equivalent to:</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> s1<span class="token punctuation">,</span> s2
<span class="token keyword">into</span> root<span class="token punctuation">.</span>sg_copy<span class="token punctuation">.</span>d1<span class="token punctuation">(</span>s1<span class="token punctuation">)</span><span class="token punctuation">,</span> root<span class="token punctuation">.</span>sg_copy<span class="token punctuation">.</span>d2<span class="token punctuation">(</span>s1<span class="token punctuation">)</span><span class="token punctuation">,</span> root<span class="token punctuation">.</span>sg_copy<span class="token punctuation">.</span>d1<span class="token punctuation">(</span>s2<span class="token punctuation">)</span><span class="token punctuation">,</span> root<span class="token punctuation">.</span>sg_copy<span class="token punctuation">.</span>d2<span class="token punctuation">(</span>s2<span class="token punctuation">)</span>
<span class="token keyword">from</span> root<span class="token punctuation">.</span>sg<span class="token punctuation">.</span>d1<span class="token punctuation">,</span> root<span class="token punctuation">.</span>sg<span class="token punctuation">.</span>d2<span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>As you can see, the statement is not very simplified in this case.</p><h6 id="_2-the-target-device-uses-variable-placeholders-the-target-measurement-list-does-not-use-variable-placeholders" tabindex="-1"><a class="header-anchor" href="#_2-the-target-device-uses-variable-placeholders-the-target-measurement-list-does-not-use-variable-placeholders"><span>(2) The target device uses variable placeholders &amp; the target measurement list does not use variable placeholders</span></a></h6><p><strong>Limitations:</strong> The number of target measurements in all <code>intoItem</code> is the same as the number of columns in the query result set.</p><p><strong>Matching method:</strong> The target measurement is specified for each query time series, and the target device is generated according to the target device placeholder of the <code>intoItem</code> where the corresponding target measurement is located.</p><p><strong>Example:</strong></p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> d1<span class="token punctuation">.</span>s1<span class="token punctuation">,</span> d1<span class="token punctuation">.</span>s2<span class="token punctuation">,</span> d2<span class="token punctuation">.</span>s3<span class="token punctuation">,</span> d3<span class="token punctuation">.</span>s4
<span class="token keyword">into</span> ::<span class="token punctuation">(</span>s1_1<span class="token punctuation">,</span> s2_2<span class="token punctuation">)</span><span class="token punctuation">,</span> root<span class="token punctuation">.</span>sg<span class="token punctuation">.</span>d2_2<span class="token punctuation">(</span>s3_3<span class="token punctuation">)</span><span class="token punctuation">,</span> root<span class="token punctuation">.</span>${<span class="token number">2</span>}_copy<span class="token punctuation">.</span>::<span class="token punctuation">(</span>s4<span class="token punctuation">)</span>
<span class="token keyword">from</span> root<span class="token punctuation">.</span>sg<span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><h6 id="_3-the-target-device-uses-variable-placeholders-the-target-measurement-list-uses-variable-placeholders" tabindex="-1"><a class="header-anchor" href="#_3-the-target-device-uses-variable-placeholders-the-target-measurement-list-uses-variable-placeholders"><span>(3) The target device uses variable placeholders &amp; the target measurement list uses variable placeholders</span></a></h6><p><strong>Limitations:</strong> There is only one <code>intoItem</code>, and the length of the list of measurement list is 1.</p><p><strong>Matching method:</strong> Each query time series can get a target time series according to the variable placeholder.</p><p><strong>Example:</strong></p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> <span class="token operator">*</span> <span class="token keyword">into</span> root<span class="token punctuation">.</span>sg_bk<span class="token punctuation">.</span>::<span class="token punctuation">(</span>::<span class="token punctuation">)</span> <span class="token keyword">from</span> root<span class="token punctuation">.</span>sg<span class="token punctuation">.</span><span class="token operator">*</span><span class="token operator">*</span><span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>Write the query results of all time series under <code>root.sg</code> to <code>root.sg_bk</code>, the device name suffix and measurement remain unchanged.</p><h5 id="align-by-device-1" tabindex="-1"><a class="header-anchor" href="#align-by-device-1"><span>ALIGN BY DEVICE</span></a></h5><blockquote><p>Note: The variable placeholder <strong>can only describe the correspondence between time series</strong>. If the query includes aggregation and expression calculation, the columns in the query result cannot correspond to a specific physical quantity, so the target measurement cannot use variable placeholders.</p></blockquote><h6 id="_1-the-target-device-does-not-use-variable-placeholders-the-target-measurement-list-uses-variable-placeholders-1" tabindex="-1"><a class="header-anchor" href="#_1-the-target-device-does-not-use-variable-placeholders-the-target-measurement-list-uses-variable-placeholders-1"><span>(1) The target device does not use variable placeholders &amp; the target measurement list uses variable placeholders</span></a></h6><p><strong>Limitations:</strong> In each <code>intoItem</code>, if the list of measurement uses variable placeholders, the length of the list must be 1.</p><p><strong>Matching method:</strong> Each query time series specifies the target device, and the target measurement is generated from the variable placeholder.</p><p><strong>Example:</strong></p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> s1<span class="token punctuation">,</span> s2<span class="token punctuation">,</span> s3<span class="token punctuation">,</span> s4
<span class="token keyword">into</span> root<span class="token punctuation">.</span>backup_sg<span class="token punctuation">.</span>d1<span class="token punctuation">(</span>s1<span class="token punctuation">,</span> s2<span class="token punctuation">,</span> s3<span class="token punctuation">,</span> s4<span class="token punctuation">)</span><span class="token punctuation">,</span> root<span class="token punctuation">.</span>backup_sg<span class="token punctuation">.</span>d2<span class="token punctuation">(</span>::<span class="token punctuation">)</span><span class="token punctuation">,</span> root<span class="token punctuation">.</span>sg<span class="token punctuation">.</span>d3<span class="token punctuation">(</span>backup_${<span class="token number">4</span>}<span class="token punctuation">)</span>
<span class="token keyword">from</span> root<span class="token punctuation">.</span>sg<span class="token punctuation">.</span>d1<span class="token punctuation">,</span> root<span class="token punctuation">.</span>sg<span class="token punctuation">.</span>d2<span class="token punctuation">,</span> root<span class="token punctuation">.</span>sg<span class="token punctuation">.</span>d3
align <span class="token keyword">by</span> device<span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><h6 id="_2-the-target-device-uses-variable-placeholders-the-target-measurement-list-does-not-use-variable-placeholders-1" tabindex="-1"><a class="header-anchor" href="#_2-the-target-device-uses-variable-placeholders-the-target-measurement-list-does-not-use-variable-placeholders-1"><span>(2) The target device uses variable placeholders &amp; the target measurement list does not use variable placeholders</span></a></h6><p><strong>Limitations:</strong> There is only one <code>intoItem</code>. (If there are multiple <code>intoItem</code> with placeholders, we will not know which source devices each <code>intoItem</code> needs to match)</p><p><strong>Matching method:</strong> Each query device obtains a target device according to the variable placeholder, and the target measurement written in each column of the result set under each device is specified by the target measurement list.</p><p><strong>Example:</strong></p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> <span class="token function">avg</span><span class="token punctuation">(</span>s1<span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token function">sum</span><span class="token punctuation">(</span>s2<span class="token punctuation">)</span> <span class="token operator">+</span> <span class="token function">sum</span><span class="token punctuation">(</span>s3<span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token function">count</span><span class="token punctuation">(</span>s4<span class="token punctuation">)</span>
<span class="token keyword">into</span> root<span class="token punctuation">.</span>agg_${<span class="token number">2</span>}<span class="token punctuation">.</span>::<span class="token punctuation">(</span>avg_s1<span class="token punctuation">,</span> sum_s2_add_s3<span class="token punctuation">,</span> count_s4<span class="token punctuation">)</span>
<span class="token keyword">from</span> root<span class="token punctuation">.</span><span class="token operator">*</span><span class="token operator">*</span>
align <span class="token keyword">by</span> device<span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><h6 id="_3-the-target-device-uses-variable-placeholders-the-target-measurement-list-uses-variable-placeholders-1" tabindex="-1"><a class="header-anchor" href="#_3-the-target-device-uses-variable-placeholders-the-target-measurement-list-uses-variable-placeholders-1"><span>(3) The target device uses variable placeholders &amp; the target measurement list uses variable placeholders</span></a></h6><p><strong>Limitations:</strong> There is only one <code>intoItem</code> and the length of the target measurement list is 1.</p><p><strong>Matching method:</strong> Each query time series can get a target time series according to the variable placeholder.</p><p><strong>Example:</strong></p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> <span class="token operator">*</span> <span class="token keyword">into</span> ::<span class="token punctuation">(</span>backup_${<span class="token number">4</span>}<span class="token punctuation">)</span> <span class="token keyword">from</span> root<span class="token punctuation">.</span>sg<span class="token punctuation">.</span><span class="token operator">*</span><span class="token operator">*</span> align <span class="token keyword">by</span> device<span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>Write the query result of each time series in <code>root.sg</code> to the same device, and add <code>backup_</code> before the measurement.</p><h4 id="specify-the-target-time-series-as-the-aligned-time-series" tabindex="-1"><a class="header-anchor" href="#specify-the-target-time-series-as-the-aligned-time-series"><span>Specify the target time series as the aligned time series</span></a></h4><p>We can use the <code>ALIGNED</code> keyword to specify the target device for writing to be aligned, and each <code>intoItem</code> can be set independently.</p><p><strong>Example:</strong></p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> s1<span class="token punctuation">,</span> s2 <span class="token keyword">into</span> root<span class="token punctuation">.</span>sg_copy<span class="token punctuation">.</span>d1<span class="token punctuation">(</span>t1<span class="token punctuation">,</span> t2<span class="token punctuation">)</span><span class="token punctuation">,</span> aligned root<span class="token punctuation">.</span>sg_copy<span class="token punctuation">.</span>d2<span class="token punctuation">(</span>t1<span class="token punctuation">,</span> t2<span class="token punctuation">)</span> <span class="token keyword">from</span> root<span class="token punctuation">.</span>sg<span class="token punctuation">.</span>d1<span class="token punctuation">,</span> root<span class="token punctuation">.</span>sg<span class="token punctuation">.</span>d2 align <span class="token keyword">by</span> device<span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>This statement specifies that <code>root.sg_copy.d1</code> is an unaligned device and <code>root.sg_copy.d2</code> is an aligned device.</p><h4 id="unsupported-query-clauses" tabindex="-1"><a class="header-anchor" href="#unsupported-query-clauses"><span>Unsupported query clauses</span></a></h4><ul><li><code>SLIMIT</code>, <code>SOFFSET</code>: The query columns are uncertain, so they are not supported.</li><li><code>LAST</code>, <code>GROUP BY TAGS</code>, <code>DISABLE ALIGN</code>: The table structure is inconsistent with the writing structure, so it is not supported.</li></ul><h4 id="other-points-to-note" tabindex="-1"><a class="header-anchor" href="#other-points-to-note"><span>Other points to note</span></a></h4><ul><li>For general aggregation queries, the timestamp is meaningless, and the convention is to use 0 to store.</li><li>When the target time-series exists, the data type of the source column and the target time-series must be compatible. About data type compatibility, see the document [Data Type](../Basic-Concept/Data-Type.md#Data Type Compatibility).</li><li>When the target time series does not exist, the system automatically creates it (including the database).</li><li>When the queried time series does not exist, or the queried sequence does not have data, the target time series will not be created automatically.</li></ul><h3 id="application-examples" tabindex="-1"><a class="header-anchor" href="#application-examples"><span>Application examples</span></a></h3><h4 id="implement-iotdb-internal-etl" tabindex="-1"><a class="header-anchor" href="#implement-iotdb-internal-etl"><span>Implement IoTDB internal ETL</span></a></h4><p>ETL the original data and write a new time series.</p><div class="language-bash line-numbers-mode" data-ext="sh" data-title="sh"><pre class="language-bash"><code>IOTDB <span class="token operator">&gt;</span> SELECT preprocess_udf<span class="token punctuation">(</span>s1, s2<span class="token punctuation">)</span> INTO ::<span class="token punctuation">(</span>preprocessed_s1, preprocessed_s2<span class="token punctuation">)</span> FROM root.sg.* ALIGN BY DEIVCE<span class="token punctuation">;</span>
+--------------+-------------------+---------------------------+--------+
<span class="token operator">|</span> <span class="token builtin class-name">source</span> device<span class="token operator">|</span>      <span class="token builtin class-name">source</span> <span class="token function">column</span><span class="token operator">|</span>          target timeseries<span class="token operator">|</span> written<span class="token operator">|</span>
+--------------+-------------------+---------------------------+--------+
<span class="token operator">|</span>    root.sg.d1<span class="token operator">|</span> preprocess_udf<span class="token punctuation">(</span>s1<span class="token punctuation">)</span><span class="token operator">|</span> root.sg.d1.preprocessed_s1<span class="token operator">|</span>    <span class="token number">8000</span><span class="token operator">|</span>
+--------------+-------------------+---------------------------+--------+
<span class="token operator">|</span>    root.sg.d1<span class="token operator">|</span> preprocess_udf<span class="token punctuation">(</span>s2<span class="token punctuation">)</span><span class="token operator">|</span> root.sg.d1.preprocessed_s2<span class="token operator">|</span>   <span class="token number">10000</span><span class="token operator">|</span>
+--------------+-------------------+---------------------------+--------+
<span class="token operator">|</span>    root.sg.d2<span class="token operator">|</span> preprocess_udf<span class="token punctuation">(</span>s1<span class="token punctuation">)</span><span class="token operator">|</span> root.sg.d2.preprocessed_s1<span class="token operator">|</span>   <span class="token number">11000</span><span class="token operator">|</span>
+--------------+-------------------+---------------------------+--------+
<span class="token operator">|</span>    root.sg.d2<span class="token operator">|</span> preprocess_udf<span class="token punctuation">(</span>s2<span class="token punctuation">)</span><span class="token operator">|</span> root.sg.d2.preprocessed_s2<span class="token operator">|</span>    <span class="token number">9000</span><span class="token operator">|</span>
+--------------+-------------------+---------------------------+--------+
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><h4 id="query-result-storage" tabindex="-1"><a class="header-anchor" href="#query-result-storage"><span>Query result storage</span></a></h4><p>Persistently store the query results, which acts like a materialized view.</p><div class="language-bash line-numbers-mode" data-ext="sh" data-title="sh"><pre class="language-bash"><code>IOTDB <span class="token operator">&gt;</span> SELECT count<span class="token punctuation">(</span>s1<span class="token punctuation">)</span>, last_value<span class="token punctuation">(</span>s1<span class="token punctuation">)</span> INTO root.sg.agg_<span class="token variable">${2}</span><span class="token punctuation">(</span>count_s1, last_value_s1<span class="token punctuation">)</span> FROM root.sg1.d1 GROUP BY <span class="token punctuation">(</span><span class="token punctuation">[</span><span class="token number">0</span>, <span class="token number">10000</span><span class="token punctuation">)</span>, 10ms<span class="token punctuation">)</span><span class="token punctuation">;</span>
+--------------------------+-----------------------------+--------+
<span class="token operator">|</span>             <span class="token builtin class-name">source</span> <span class="token function">column</span><span class="token operator">|</span>            target timeseries<span class="token operator">|</span> written<span class="token operator">|</span>
+--------------------------+-----------------------------+--------+
<span class="token operator">|</span>      count<span class="token punctuation">(</span>root.sg.d1.s1<span class="token punctuation">)</span><span class="token operator">|</span>      root.sg.agg_d1.count_s1<span class="token operator">|</span>    <span class="token number">1000</span><span class="token operator">|</span>
+--------------------------+-----------------------------+--------+
<span class="token operator">|</span> last_value<span class="token punctuation">(</span>root.sg.d1.s2<span class="token punctuation">)</span><span class="token operator">|</span> root.sg.agg_d1.last_value_s2<span class="token operator">|</span>    <span class="token number">1000</span><span class="token operator">|</span>
+--------------------------+-----------------------------+--------+
Total line number <span class="token operator">=</span> <span class="token number">2</span>
It costs <span class="token number">0</span>.115s
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><h4 id="non-aligned-time-series-to-aligned-time-series" tabindex="-1"><a class="header-anchor" href="#non-aligned-time-series-to-aligned-time-series"><span>Non-aligned time series to aligned time series</span></a></h4><p>Rewrite non-aligned time series into another aligned time series.</p><p><strong>Note:</strong> It is recommended to use the <code>LIMIT &amp; OFFSET</code> clause or the <code>WHERE</code> clause (time filter) to batch data to prevent excessive data volume in a single operation.</p><div class="language-bash line-numbers-mode" data-ext="sh" data-title="sh"><pre class="language-bash"><code>IOTDB <span class="token operator">&gt;</span> SELECT s1, s2 INTO ALIGNED root.sg1.aligned_d<span class="token punctuation">(</span>s1, s2<span class="token punctuation">)</span> FROM root.sg1.non_aligned_d WHERE <span class="token function">time</span> <span class="token operator">&gt;=</span> <span class="token number">0</span> and <span class="token function">time</span> <span class="token operator">&lt;</span> <span class="token number">10000</span><span class="token punctuation">;</span>
+--------------------------+----------------------+--------+
<span class="token operator">|</span>             <span class="token builtin class-name">source</span> <span class="token function">column</span><span class="token operator">|</span>     target timeseries<span class="token operator">|</span> written<span class="token operator">|</span>
+--------------------------+----------------------+--------+
<span class="token operator">|</span> root.sg1.non_aligned_d.s1<span class="token operator">|</span> root.sg1.aligned_d.s1<span class="token operator">|</span>   <span class="token number">10000</span><span class="token operator">|</span>
+--------------------------+----------------------+--------+
<span class="token operator">|</span> root.sg1.non_aligned_d.s2<span class="token operator">|</span> root.sg1.aligned_d.s2<span class="token operator">|</span>   <span class="token number">10000</span><span class="token operator">|</span>
+--------------------------+----------------------+--------+
Total line number <span class="token operator">=</span> <span class="token number">2</span>
It costs <span class="token number">0</span>.375s
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><h3 id="user-permission-management" tabindex="-1"><a class="header-anchor" href="#user-permission-management"><span>User Permission Management</span></a></h3><p>The user must have the following permissions to execute a query write-back statement:</p><ul><li>All <code>READ_TIMESERIES</code> permissions for the source series in the <code>select</code> clause.</li><li>All <code>INSERT_TIMESERIES</code> permissions for the target series in the <code>into</code> clause.</li></ul><p>For more user permissions related content, please refer to <a class="route-link" href="/UserGuide/V1.2.x/User-Manual/Security-Management.html">Account Management Statements</a>.</p><h3 id="configurable-properties" tabindex="-1"><a class="header-anchor" href="#configurable-properties"><span>Configurable Properties</span></a></h3><ul><li><code>select_into_insert_tablet_plan_row_limit</code>: The maximum number of rows can be processed in one insert-tablet-plan when executing select-into statements. 10000 by default.</li></ul></div><!--[--><!----><!--]--><footer class="vp-page-meta"><div class="vp-meta-item edit-link"><a href="https://github.com/apache/iotdb-docs/edit/main/src/UserGuide/V1.2.x/User-Manual/Query-Data.md" rel="noopener noreferrer" target="_blank" aria-label="Found Error? Edit this page on GitHub" class="nav-link vp-meta-label"><!--[--><svg xmlns="http://www.w3.org/2000/svg" class="icon edit-icon" viewBox="0 0 1024 1024" fill="currentColor" aria-label="edit icon"><path d="M430.818 653.65a60.46 60.46 0 0 1-50.96-93.281l71.69-114.012 7.773-10.365L816.038 80.138A60.46 60.46 0 0 1 859.225 62a60.46 60.46 0 0 1 43.186 18.138l43.186 43.186a60.46 60.46 0 0 1 0 86.373L588.879 565.55l-8.637 8.637-117.466 68.234a60.46 60.46 0 0 1-31.958 11.229z"></path><path d="M728.802 962H252.891A190.883 190.883 0 0 1 62.008 771.98V296.934a190.883 190.883 0 0 1 190.883-192.61h267.754a60.46 60.46 0 0 1 0 120.92H252.891a69.962 69.962 0 0 0-69.098 69.099V771.98a69.962 69.962 0 0 0 69.098 69.098h475.911A69.962 69.962 0 0 0 797.9 771.98V503.363a60.46 60.46 0 1 1 120.922 0V771.98A190.883 190.883 0 0 1 728.802 962z"></path></svg><!--]-->Found Error? Edit this page on GitHub<span><svg class="external-link-icon" xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path><polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg><span class="external-link-icon-sr-only">open in new window</span></span><!----></a></div><div class="vp-meta-item git-info"><div class="update-time"><span class="vp-meta-label">Last update: </span><!----></div><!----></div></footer><nav class="vp-page-nav"><a class="route-link nav-link prev" href="/UserGuide/V1.2.x/User-Manual/Write-Delete-Data.html" aria-label="Write Delete Data"><div class="hint"><span class="arrow start"></span>Prev</div><div class="link"><!---->Write Delete Data</div></a><a class="route-link nav-link next" href="/UserGuide/V1.2.x/User-Manual/Operator-and-Expression.html" aria-label="Operator and Expression"><div class="hint">Next<span class="arrow end"></span></div><div class="link">Operator and Expression<!----></div></a></nav><!----><!--[--><!----><!--]--><!--]--></main><!--]--><footer style="padding-bottom:2rem;"><span id="doc-version" style="display:none;">rel/1.2</span><p style="text-align:center;color:#909399;font-size:12px;margin:0 30px;">Copyright © 2024 The Apache Software Foundation.<br> Apache and the Apache feather logo are trademarks of The Apache Software Foundation</p><p style="text-align:center;margin-top:10px;color:#909399;font-size:12px;margin:0 30px;"><strong>Have a question?</strong> Connect with us on QQ, WeChat, or Slack. <a href="https://github.com/apache/iotdb/issues/1995">Join the community</a> now.</p></footer></div><!--]--><!--]--><!--[--><!----><!--]--><!--]--></div>
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