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end"></span></button><!----></section></li><li><section class="sidebar-group"><button class="sidebar-heading clickable"><!----><span class="title">Quick Start</span><span class="arrow end"></span></button><!----></section></li><li><section class="sidebar-group"><button class="sidebar-heading clickable"><!----><span class="title">Data Concept</span><span class="arrow end"></span></button><!----></section></li><li><section class="sidebar-group"><button class="sidebar-heading clickable"><!----><span class="title">Syntax Conventions</span><span class="arrow end"></span></button><!----></section></li><li><section class="sidebar-group"><button class="sidebar-heading clickable"><!----><span class="title">API</span><span class="arrow end"></span></button><!----></section></li><li><section class="sidebar-group"><button class="sidebar-heading clickable"><!----><span class="title">Operate Metadata</span><span class="arrow end"></span></button><!----></section></li><li><section 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router-link-exact-active nav-link sidebar-link heading" aria-label="Syntax Definition"><!---->Syntax Definition<!----></a><ul class="sidebar-sub-headers"></ul></li><li class="sidebar-sub-header"><a aria-current="page" href="/UserGuide/V1.2.x/Query-Data/Overview.html#syntax-description" class="router-link-active router-link-exact-active nav-link sidebar-link heading" aria-label="Syntax Description"><!---->Syntax Description<!----></a><ul class="sidebar-sub-headers"><li class="sidebar-sub-header"><a aria-current="page" href="/UserGuide/V1.2.x/Query-Data/Overview.html#select-clause" class="router-link-active router-link-exact-active nav-link sidebar-link heading" aria-label="SELECT clause"><!---->SELECT clause<!----></a><ul class="sidebar-sub-headers"></ul></li><li class="sidebar-sub-header"><a aria-current="page" href="/UserGuide/V1.2.x/Query-Data/Overview.html#into-clause" class="router-link-active router-link-exact-active nav-link sidebar-link heading" aria-label="INTO clause"><!---->INTO clause<!----></a><ul class="sidebar-sub-headers"></ul></li><li class="sidebar-sub-header"><a aria-current="page" href="/UserGuide/V1.2.x/Query-Data/Overview.html#from-clause" class="router-link-active router-link-exact-active nav-link sidebar-link heading" aria-label="FROM clause"><!---->FROM clause<!----></a><ul class="sidebar-sub-headers"></ul></li><li class="sidebar-sub-header"><a aria-current="page" href="/UserGuide/V1.2.x/Query-Data/Overview.html#where-clause" class="router-link-active router-link-exact-active nav-link sidebar-link heading" aria-label="WHERE clause"><!---->WHERE clause<!----></a><ul class="sidebar-sub-headers"></ul></li><li class="sidebar-sub-header"><a aria-current="page" href="/UserGuide/V1.2.x/Query-Data/Overview.html#group-by-clause" class="router-link-active router-link-exact-active nav-link sidebar-link heading" aria-label="GROUP BY clause"><!---->GROUP BY clause<!----></a><ul class="sidebar-sub-headers"></ul></li><li class="sidebar-sub-header"><a aria-current="page" href="/UserGuide/V1.2.x/Query-Data/Overview.html#having-clause" class="router-link-active router-link-exact-active nav-link sidebar-link heading" aria-label="HAVING clause"><!---->HAVING clause<!----></a><ul class="sidebar-sub-headers"></ul></li><li class="sidebar-sub-header"><a aria-current="page" href="/UserGuide/V1.2.x/Query-Data/Overview.html#order-by-clause" class="router-link-active router-link-exact-active nav-link sidebar-link heading" aria-label="ORDER BY clause"><!---->ORDER BY clause<!----></a><ul class="sidebar-sub-headers"></ul></li><li class="sidebar-sub-header"><a aria-current="page" href="/UserGuide/V1.2.x/Query-Data/Overview.html#fill-clause" class="router-link-active router-link-exact-active nav-link sidebar-link heading" aria-label="FILL clause"><!---->FILL clause<!----></a><ul class="sidebar-sub-headers"></ul></li><li class="sidebar-sub-header"><a aria-current="page" href="/UserGuide/V1.2.x/Query-Data/Overview.html#slimit-and-soffset-clauses" class="router-link-active router-link-exact-active nav-link sidebar-link heading" aria-label="SLIMIT and SOFFSET clauses"><!---->SLIMIT and SOFFSET clauses<!----></a><ul class="sidebar-sub-headers"></ul></li><li class="sidebar-sub-header"><a aria-current="page" href="/UserGuide/V1.2.x/Query-Data/Overview.html#limit-and-offset-clauses" class="router-link-active router-link-exact-active nav-link sidebar-link heading" aria-label="LIMIT and OFFSET clauses"><!---->LIMIT and OFFSET clauses<!----></a><ul class="sidebar-sub-headers"></ul></li><li class="sidebar-sub-header"><a aria-current="page" href="/UserGuide/V1.2.x/Query-Data/Overview.html#align-by-clause" class="router-link-active router-link-exact-active nav-link sidebar-link heading" aria-label="ALIGN BY clause"><!---->ALIGN BY clause<!----></a><ul class="sidebar-sub-headers"></ul></li></ul></li><li class="sidebar-sub-header"><a aria-current="page" href="/UserGuide/V1.2.x/Query-Data/Overview.html#basic-examples" class="router-link-active router-link-exact-active nav-link sidebar-link heading" aria-label="Basic Examples"><!---->Basic Examples<!----></a><ul class="sidebar-sub-headers"><li class="sidebar-sub-header"><a aria-current="page" href="/UserGuide/V1.2.x/Query-Data/Overview.html#select-a-column-of-data-based-on-a-time-interval" class="router-link-active router-link-exact-active nav-link sidebar-link heading" aria-label="Select a Column of Data Based on a Time Interval"><!---->Select a Column of Data Based on a Time Interval<!----></a><ul class="sidebar-sub-headers"></ul></li><li class="sidebar-sub-header"><a aria-current="page" href="/UserGuide/V1.2.x/Query-Data/Overview.html#select-multiple-columns-of-data-based-on-a-time-interval" class="router-link-active router-link-exact-active nav-link sidebar-link heading" aria-label="Select Multiple Columns of Data Based on a Time Interval"><!---->Select Multiple Columns of Data Based on a Time Interval<!----></a><ul class="sidebar-sub-headers"></ul></li><li class="sidebar-sub-header"><a aria-current="page" href="/UserGuide/V1.2.x/Query-Data/Overview.html#select-multiple-columns-of-data-for-the-same-device-according-to-multiple-time-intervals" class="router-link-active router-link-exact-active nav-link sidebar-link heading" aria-label="Select Multiple Columns of Data for the Same Device According to Multiple Time Intervals"><!---->Select Multiple Columns of Data for the Same Device According to Multiple Time Intervals<!----></a><ul class="sidebar-sub-headers"></ul></li><li class="sidebar-sub-header"><a aria-current="page" href="/UserGuide/V1.2.x/Query-Data/Overview.html#choose-multiple-columns-of-data-for-different-devices-according-to-multiple-time-intervals" class="router-link-active router-link-exact-active nav-link sidebar-link heading" aria-label="Choose Multiple Columns of Data for Different Devices According to Multiple Time Intervals"><!---->Choose Multiple Columns of Data for Different Devices According to Multiple Time Intervals<!----></a><ul class="sidebar-sub-headers"></ul></li><li class="sidebar-sub-header"><a aria-current="page" href="/UserGuide/V1.2.x/Query-Data/Overview.html#order-by-time-query" class="router-link-active router-link-exact-active nav-link sidebar-link heading" aria-label="Order By Time Query"><!---->Order By Time Query<!----></a><ul class="sidebar-sub-headers"></ul></li></ul></li><li class="sidebar-sub-header"><a aria-current="page" href="/UserGuide/V1.2.x/Query-Data/Overview.html#execution-interface" class="router-link-active router-link-exact-active nav-link sidebar-link heading" aria-label="Execution Interface"><!---->Execution Interface<!----></a><ul class="sidebar-sub-headers"><li class="sidebar-sub-header"><a aria-current="page" href="/UserGuide/V1.2.x/Query-Data/Overview.html#execute-queries-using-iotdb-sql" class="router-link-active router-link-exact-active nav-link sidebar-link heading" aria-label="Execute queries using IoTDB-SQL"><!---->Execute queries using IoTDB-SQL<!----></a><ul class="sidebar-sub-headers"></ul></li><li class="sidebar-sub-header"><a aria-current="page" href="/UserGuide/V1.2.x/Query-Data/Overview.html#efficient-execution-interfaces" class="router-link-active router-link-exact-active nav-link sidebar-link heading" aria-label="Efficient execution interfaces"><!---->Efficient execution interfaces<!----></a><ul class="sidebar-sub-headers"></ul></li></ul></li></ul><!--]--></li><li><!--[--><a href="/UserGuide/V1.2.x/Query-Data/Select-Expression.html" class="nav-link sidebar-link sidebar-page" aria-label="Select Expression"><!---->Select Expression<!----></a><ul class="sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a href="/UserGuide/V1.2.x/Query-Data/Last-Query.html" class="nav-link sidebar-link sidebar-page" aria-label="Last Query"><!---->Last Query<!----></a><ul class="sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a href="/UserGuide/V1.2.x/Query-Data/Align-By.html" class="nav-link sidebar-link sidebar-page" aria-label="Query Alignment Mode"><!---->Query Alignment Mode<!----></a><ul class="sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a href="/UserGuide/V1.2.x/Query-Data/Where-Condition.html" class="nav-link sidebar-link sidebar-page" aria-label="Where Condition"><!---->Where Condition<!----></a><ul class="sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a href="/UserGuide/V1.2.x/Query-Data/Group-By.html" class="nav-link sidebar-link sidebar-page" aria-label="Group By"><!---->Group By<!----></a><ul class="sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a href="/UserGuide/V1.2.x/Query-Data/Having-Condition.html" class="nav-link sidebar-link sidebar-page" aria-label="Having Condition"><!---->Having Condition<!----></a><ul class="sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a href="/UserGuide/V1.2.x/Query-Data/Fill.html" class="nav-link sidebar-link sidebar-page" aria-label="Fill Null Value"><!---->Fill Null Value<!----></a><ul class="sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a href="/UserGuide/V1.2.x/Query-Data/Pagination.html" class="nav-link sidebar-link sidebar-page" aria-label="Pagination"><!---->Pagination<!----></a><ul class="sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a href="/UserGuide/V1.2.x/Query-Data/Select-Into.html" class="nav-link sidebar-link sidebar-page" aria-label="Select Into"><!---->Select Into<!----></a><ul class="sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a href="/UserGuide/V1.2.x/Query-Data/Continuous-Query.html" class="nav-link sidebar-link sidebar-page" aria-label="Continuous Query"><!---->Continuous Query<!----></a><ul class="sidebar-sub-headers"></ul><!--]--></li></ul></section></li><li><section class="sidebar-group"><button class="sidebar-heading clickable"><!----><span class="title">Operators and Functions</span><span class="arrow end"></span></button><!----></section></li><li><section class="sidebar-group"><button class="sidebar-heading clickable"><!----><span class="title">Trigger</span><span class="arrow end"></span></button><!----></section></li><li><section class="sidebar-group"><button class="sidebar-heading clickable"><!----><span class="title">Monitor and Alert</span><span class="arrow end"></span></button><!----></section></li><li><section class="sidebar-group"><button class="sidebar-heading clickable"><!----><span class="title">Administration Management</span><span class="arrow end"></span></button><!----></section></li><li><section class="sidebar-group"><button class="sidebar-heading clickable"><!----><span class="title">Maintenance Tools</span><span class="arrow end"></span></button><!----></section></li><li><section class="sidebar-group"><button class="sidebar-heading clickable"><!----><span class="title">Collaboration of Edge and Cloud</span><span class="arrow end"></span></button><!----></section></li><li><section class="sidebar-group"><button class="sidebar-heading clickable"><!----><span class="title">Ecosystem Integration</span><span class="arrow end"></span></button><!----></section></li><li><section class="sidebar-group"><button class="sidebar-heading clickable"><!----><span class="title">Cluster</span><span class="arrow end"></span></button><!----></section></li><li><section class="sidebar-group"><button class="sidebar-heading clickable"><!----><span class="title">FAQ</span><span class="arrow end"></span></button><!----></section></li><li><section class="sidebar-group"><button class="sidebar-heading clickable"><!----><span class="title">Reference</span><span class="arrow end"></span></button><!----></section></li></ul><!--[--><!----><!--]--></aside><!--[--><main class="page" id="main-content"><!--[--><!----><nav class="breadcrumb disable"></nav><div class="page-title"><h1><!---->Overview</h1><div class="page-info"><!----><!----><!----><!----><span class="page-reading-time-info" aria-label="Reading Time"><svg xmlns="http://www.w3.org/2000/svg" class="icon timer-icon" viewBox="0 0 1024 1024" fill="currentColor" aria-label="timer icon"><path d="M799.387 122.15c4.402-2.978 7.38-7.897 7.38-13.463v-1.165c0-8.933-7.38-16.312-16.312-16.312H256.33c-8.933 0-16.311 7.38-16.311 16.312v1.165c0 5.825 2.977 10.874 7.637 13.592 4.143 194.44 97.22 354.963 220.201 392.763-122.204 37.542-214.893 196.511-220.2 389.397-4.661 5.049-7.638 11.651-7.638 19.03v5.825h566.49v-5.825c0-7.379-2.849-13.981-7.509-18.9-5.049-193.016-97.867-351.985-220.2-389.527 123.24-37.67 216.446-198.453 220.588-392.892zM531.16 450.445v352.632c117.674 1.553 211.787 40.778 211.787 88.676H304.097c0-48.286 95.149-87.382 213.728-88.676V450.445c-93.077-3.107-167.901-81.297-167.901-177.093 0-8.803 6.99-15.793 15.793-15.793 8.803 0 15.794 6.99 15.794 15.793 0 80.261 63.69 145.635 142.01 145.635s142.011-65.374 142.011-145.635c0-8.803 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 8 min</span><meta property="timeRequired" content="PT8M"></span><!----><!----></div><hr></div><div class="toc-place-holder"><aside id="toc"><!--[--><!----><!--]--><div class="toc-header">On This Page<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><div class="toc-wrapper"><ul class="toc-list"><!--[--><li class="toc-item"><a aria-current="page" href="/UserGuide/V1.2.x/Query-Data/Overview.html#syntax-definition" class="router-link-active router-link-exact-active toc-link level2">Syntax Definition</a></li><!----><!--]--><!--[--><li class="toc-item"><a aria-current="page" href="/UserGuide/V1.2.x/Query-Data/Overview.html#syntax-description" class="router-link-active router-link-exact-active toc-link level2">Syntax Description</a></li><ul class="toc-list"><!--[--><li class="toc-item"><a aria-current="page" href="/UserGuide/V1.2.x/Query-Data/Overview.html#select-clause" class="router-link-active router-link-exact-active toc-link level3">SELECT clause</a></li><!----><!--]--><!--[--><li class="toc-item"><a aria-current="page" href="/UserGuide/V1.2.x/Query-Data/Overview.html#into-clause" class="router-link-active router-link-exact-active toc-link level3">INTO clause</a></li><!----><!--]--><!--[--><li class="toc-item"><a aria-current="page" href="/UserGuide/V1.2.x/Query-Data/Overview.html#from-clause" class="router-link-active router-link-exact-active toc-link level3">FROM clause</a></li><!----><!--]--><!--[--><li class="toc-item"><a aria-current="page" href="/UserGuide/V1.2.x/Query-Data/Overview.html#where-clause" class="router-link-active router-link-exact-active toc-link level3">WHERE clause</a></li><!----><!--]--><!--[--><li class="toc-item"><a aria-current="page" href="/UserGuide/V1.2.x/Query-Data/Overview.html#group-by-clause" class="router-link-active router-link-exact-active toc-link level3">GROUP BY clause</a></li><!----><!--]--><!--[--><li class="toc-item"><a aria-current="page" href="/UserGuide/V1.2.x/Query-Data/Overview.html#having-clause" class="router-link-active router-link-exact-active toc-link level3">HAVING clause</a></li><!----><!--]--><!--[--><li class="toc-item"><a aria-current="page" href="/UserGuide/V1.2.x/Query-Data/Overview.html#order-by-clause" class="router-link-active router-link-exact-active toc-link level3">ORDER BY clause</a></li><!----><!--]--><!--[--><li class="toc-item"><a aria-current="page" href="/UserGuide/V1.2.x/Query-Data/Overview.html#fill-clause" class="router-link-active router-link-exact-active toc-link level3">FILL clause</a></li><!----><!--]--><!--[--><li class="toc-item"><a aria-current="page" href="/UserGuide/V1.2.x/Query-Data/Overview.html#slimit-and-soffset-clauses" class="router-link-active router-link-exact-active toc-link level3">SLIMIT and SOFFSET clauses</a></li><!----><!--]--><!--[--><li class="toc-item"><a aria-current="page" href="/UserGuide/V1.2.x/Query-Data/Overview.html#limit-and-offset-clauses" class="router-link-active router-link-exact-active toc-link level3">LIMIT and OFFSET clauses</a></li><!----><!--]--><!--[--><li class="toc-item"><a aria-current="page" href="/UserGuide/V1.2.x/Query-Data/Overview.html#align-by-clause" class="router-link-active router-link-exact-active toc-link level3">ALIGN BY clause</a></li><!----><!--]--></ul><!--]--><!--[--><li class="toc-item"><a aria-current="page" href="/UserGuide/V1.2.x/Query-Data/Overview.html#basic-examples" class="router-link-active router-link-exact-active toc-link level2">Basic Examples</a></li><ul class="toc-list"><!--[--><li class="toc-item"><a aria-current="page" href="/UserGuide/V1.2.x/Query-Data/Overview.html#select-a-column-of-data-based-on-a-time-interval" class="router-link-active router-link-exact-active toc-link level3">Select a Column of Data Based on a Time Interval</a></li><!----><!--]--><!--[--><li class="toc-item"><a aria-current="page" href="/UserGuide/V1.2.x/Query-Data/Overview.html#select-multiple-columns-of-data-based-on-a-time-interval" class="router-link-active router-link-exact-active toc-link level3">Select Multiple Columns of Data Based on a Time Interval</a></li><!----><!--]--><!--[--><li class="toc-item"><a aria-current="page" href="/UserGuide/V1.2.x/Query-Data/Overview.html#select-multiple-columns-of-data-for-the-same-device-according-to-multiple-time-intervals" class="router-link-active router-link-exact-active toc-link level3">Select Multiple Columns of Data for the Same Device According to Multiple Time Intervals</a></li><!----><!--]--><!--[--><li class="toc-item"><a aria-current="page" href="/UserGuide/V1.2.x/Query-Data/Overview.html#choose-multiple-columns-of-data-for-different-devices-according-to-multiple-time-intervals" class="router-link-active router-link-exact-active toc-link level3">Choose Multiple Columns of Data for Different Devices According to Multiple Time Intervals</a></li><!----><!--]--><!--[--><li class="toc-item"><a aria-current="page" href="/UserGuide/V1.2.x/Query-Data/Overview.html#order-by-time-query" class="router-link-active router-link-exact-active toc-link level3">Order By Time Query</a></li><!----><!--]--></ul><!--]--><!--[--><li class="toc-item"><a aria-current="page" href="/UserGuide/V1.2.x/Query-Data/Overview.html#execution-interface" class="router-link-active router-link-exact-active toc-link level2">Execution Interface</a></li><ul class="toc-list"><!--[--><li class="toc-item"><a aria-current="page" href="/UserGuide/V1.2.x/Query-Data/Overview.html#execute-queries-using-iotdb-sql" class="router-link-active router-link-exact-active toc-link level3">Execute queries using IoTDB-SQL</a></li><!----><!--]--><!--[--><li class="toc-item"><a aria-current="page" href="/UserGuide/V1.2.x/Query-Data/Overview.html#efficient-execution-interfaces" class="router-link-active router-link-exact-active toc-link level3">Efficient execution interfaces</a></li><!----><!--]--></ul><!--]--></ul></div><!--[--><!----><!--]--></aside></div><!----><div class="theme-hope-content"><!--
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--><h1 id="overview" tabindex="-1"><a class="header-anchor" href="#overview" aria-hidden="true">#</a> Overview</h1><h2 id="syntax-definition" tabindex="-1"><a class="header-anchor" href="#syntax-definition" aria-hidden="true">#</a> Syntax Definition</h2><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"><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><h2 id="syntax-description" tabindex="-1"><a class="header-anchor" href="#syntax-description" aria-hidden="true">#</a> Syntax Description</h2><h3 id="select-clause" tabindex="-1"><a class="header-anchor" href="#select-clause" aria-hidden="true">#</a> <code>SELECT</code> clause</h3><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. For details and examples, see the document <a href="/UserGuide/V1.2.x/Query-Data/Last-Query.html" class="">Last Query</a>.</li><li>For details and examples, see the document <a href="/UserGuide/V1.2.x/Query-Data/Select-Expression.html" class="">Select Expression</a>.</li></ul><h3 id="into-clause" tabindex="-1"><a class="header-anchor" href="#into-clause" aria-hidden="true">#</a> <code>INTO</code> clause</h3><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><li>For detailed instructions and examples, see the document <a href="/UserGuide/V1.2.x/Query-Data/Select-Into.html" class="">SELECT INTO</a>.</li></ul><h3 id="from-clause" tabindex="-1"><a class="header-anchor" href="#from-clause" aria-hidden="true">#</a> <code>FROM</code> clause</h3><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><h3 id="where-clause" tabindex="-1"><a class="header-anchor" href="#where-clause" aria-hidden="true">#</a> <code>WHERE</code> clause</h3><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><li>For details and examples, see the document <a href="/UserGuide/V1.2.x/Query-Data/Where-Condition.html" class="">Where Condition</a>.</li></ul><h3 id="group-by-clause" tabindex="-1"><a class="header-anchor" href="#group-by-clause" aria-hidden="true">#</a> <code>GROUP BY</code> clause</h3><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>segmentation by time interval</strong>、<strong>group by variation</strong>、<strong>group by series</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><li>For details and examples, see the document <a href="/UserGuide/V1.2.x/Query-Data/Group-By.html" class="">Group By Aggregation</a>.</li></ul><h3 id="having-clause" tabindex="-1"><a class="header-anchor" href="#having-clause" aria-hidden="true">#</a> <code>HAVING</code> clause</h3><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><li>For details and examples, see the document <a href="/UserGuide/V1.2.x/Query-Data/Having-Condition.html" class="">Aggregation Result Filtering</a>.</li></ul><h3 id="order-by-clause" tabindex="-1"><a class="header-anchor" href="#order-by-clause" aria-hidden="true">#</a> <code>ORDER BY</code> clause</h3><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><li>For details and examples, see the document <a href="/UserGuide/V1.2.x/Query-Data/Order-By.html" class="">Order By</a>.</li></ul><h3 id="fill-clause" tabindex="-1"><a class="header-anchor" href="#fill-clause" aria-hidden="true">#</a> <code>FILL</code> clause</h3><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><li>For details and examples, see the document <a href="/UserGuide/V1.2.x/Query-Data/Fill.html" class="">Fill Null Value</a>.</li></ul><h3 id="slimit-and-soffset-clauses" tabindex="-1"><a class="header-anchor" href="#slimit-and-soffset-clauses" aria-hidden="true">#</a> <code>SLIMIT</code> and <code>SOFFSET</code> clauses</h3><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><li>For details and examples of query result pagination, see the document <a href="/UserGuide/V1.2.x/Query-Data/Pagination.html" class="">Result Set Pagination</a>.</li></ul><h3 id="limit-and-offset-clauses" tabindex="-1"><a class="header-anchor" href="#limit-and-offset-clauses" aria-hidden="true">#</a> <code>LIMIT</code> and <code>OFFSET</code> clauses</h3><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><li>For details and examples of query result pagination, see the document <a href="/UserGuide/V1.2.x/Query-Data/Pagination.html" class="">Result Set Pagination</a>.</li></ul><h3 id="align-by-clause" tabindex="-1"><a class="header-anchor" href="#align-by-clause" aria-hidden="true">#</a> <code>ALIGN BY</code> clause</h3><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><li>For details and examples, see the document <a href="/UserGuide/V1.2.x/Query-Data/Align-By.html" class="">Query Alignment Mode</a>.</li></ul><h2 id="basic-examples" tabindex="-1"><a class="header-anchor" href="#basic-examples" aria-hidden="true">#</a> Basic Examples</h2><h3 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" aria-hidden="true">#</a> Select a Column of Data Based on a Time Interval</h3><p>The SQL statement is:</p><div class="language-sql line-numbers-mode" data-ext="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"><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><h3 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" aria-hidden="true">#</a> Select Multiple Columns of Data Based on a Time Interval</h3><p>The SQL statement is:</p><div class="language-sql line-numbers-mode" data-ext="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"><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><h3 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" aria-hidden="true">#</a> Select Multiple Columns of Data for the Same Device According to Multiple Time Intervals</h3><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"><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"><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><h3 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" aria-hidden="true">#</a> Choose Multiple Columns of Data for Different Devices According to Multiple Time Intervals</h3><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"><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"><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><h3 id="order-by-time-query" tabindex="-1"><a class="header-anchor" href="#order-by-time-query" aria-hidden="true">#</a> Order By Time Query</h3><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. For example, the SQL statement is:</p><div class="language-sql line-numbers-mode" data-ext="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"><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><h2 id="execution-interface" tabindex="-1"><a class="header-anchor" href="#execution-interface" aria-hidden="true">#</a> Execution Interface</h2><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><h3 id="execute-queries-using-iotdb-sql" tabindex="-1"><a class="header-anchor" href="#execute-queries-using-iotdb-sql" aria-hidden="true">#</a> Execute queries using IoTDB-SQL</h3><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 href="/UserGuide/V1.2.x/QuickStart/Command-Line-Interface.html" class="">SQL command line terminal</a>.</p></li><li><p>Execute query statements in JDBC, see <a href="/UserGuide/V1.2.x/API/Programming-JDBC.html" class="">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"><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 href="/UserGuide/V1.2.x/API/RestServiceV1.html" class="">HTTP API V1</a> or <a href="/UserGuide/V1.2.x/API/RestServiceV2.html" class="">HTTP API V2</a> for details.</p></li></ul><h3 id="efficient-execution-interfaces" tabindex="-1"><a class="header-anchor" href="#efficient-execution-interfaces" aria-hidden="true">#</a> Efficient execution interfaces</h3><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"><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"><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"><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></div><!----><footer class="page-meta"><div class="meta-item edit-link"><a href="https://github.com/apache/iotdb/edit/rel/1.2/docs/UserGuide/Query-Data/Overview.md" rel="noopener noreferrer" target="_blank" aria-label="Found Error? Edit this page on GitHub" class="nav-link 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="meta-item git-info"><!----><!----></div></footer><nav class="page-nav"><!----><a href="/UserGuide/V1.2.x/Query-Data/Select-Expression.html" class="nav-link next" aria-label="Select Expression"><div class="hint">Next<span class="arrow end"></span></div><div class="link">Select 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 © 2023 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><p style="text-align:center;margin-top:10px;color:#909399;font-size:12px;margin:0 30px;"> We use <a href="https://analytics.google.com">Google Analytics</a> to collect anonymous, aggregated usage information. </p></footer></div><!--]--><!--]--><!----><!--]--></div>
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