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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 4 min</span><meta property="timeRequired" content="PT4M"></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="#introduction">Introduction</a></li><!----><!--]--><!--[--><li class="vp-toc-item"><a class="route-link vp-toc-link level2" href="#syntax-definition">Syntax Definition</a></li><!----><!--]--><!--[--><li class="vp-toc-item"><a class="route-link vp-toc-link level2" href="#fill-methods">Fill Methods</a></li><li><ul class="vp-toc-list"><!--[--><li class="vp-toc-item"><a class="route-link vp-toc-link level3" href="#previous-fill">PREVIOUS Fill</a></li><!----><!--]--><!--[--><li class="vp-toc-item"><a class="route-link vp-toc-link level3" href="#linear-fill">LINEAR Fill</a></li><!----><!--]--><!--[--><li class="vp-toc-item"><a class="route-link vp-toc-link level3" href="#constant-fill">Constant Fill</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="fill-null-value" tabindex="-1"><a class="header-anchor" href="#fill-null-value"><span>Fill Null Value</span></a></h1><h2 id="introduction" tabindex="-1"><a class="header-anchor" href="#introduction"><span>Introduction</span></a></h2><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><h2 id="syntax-definition" tabindex="-1"><a class="header-anchor" href="#syntax-definition"><span>Syntax Definition</span></a></h2><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><h2 id="fill-methods" tabindex="-1"><a class="header-anchor" href="#fill-methods"><span>Fill Methods</span></a></h2><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><h3 id="previous-fill" tabindex="-1"><a class="header-anchor" href="#previous-fill"><span><code>PREVIOUS</code> Fill</span></a></h3><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><h3 id="linear-fill" tabindex="-1"><a class="header-anchor" href="#linear-fill"><span><code>LINEAR</code> Fill</span></a></h3><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><h3 id="constant-fill" tabindex="-1"><a class="header-anchor" href="#constant-fill"><span>Constant Fill</span></a></h3><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></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/V1.0.x/Query-Data/Fill.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/V1.0.x/Query-Data/Having-Condition.html" aria-label="Having Condition"><div class="hint"><span class="arrow start"></span>Prev</div><div class="link"><!---->Having Condition</div></a><a class="route-link nav-link next" href="/UserGuide/V1.0.x/Query-Data/Pagination.html" aria-label="Pagination"><div class="hint">Next<span class="arrow end"></span></div><div class="link">Pagination<!----></div></a></nav><!----><!--[--><!----><!--]--><!--]--></main><!--]--><footer style="padding-bottom:2rem;"><span id="doc-version" style="display:none;">rel/1.0</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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