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       </script><title>IoTDB Website</title><meta name="description" content="查询补空值 当对序列进行分段聚合时，某一段时间可能不存在数据，则此段数据的聚合结果为空，但这种空值不利于进行数据可视化展示和分析，需要对空值进行填补。 查询补空值允许用户按照特定的方法对查询结果填充空值，如取前一个不为空的值，或线性插值。补空值之后的查询结果能更好地反映数据分布，有利于用户进行数据分析。 在 IoTDB 中，用户可以使用 FILL 子句...">
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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="#查询补空值">查询补空值</a></li><li><ul class="vp-toc-list"><!--[--><li class="vp-toc-item"><a class="route-link vp-toc-link level3" href="#填充方法">填充方法</a></li><!----><!--]--><!--[--><li class="vp-toc-item"><a class="route-link vp-toc-link level3" href="#单点补空值">单点补空值</a></li><!----><!--]--><!--[--><li class="vp-toc-item"><a class="route-link vp-toc-link level3" href="#降采样补空值">降采样补空值</a></li><!----><!--]--></ul></li><!--]--></ul><div class="vp-toc-marker" style="top:-1.7rem;"></div></div><!--[--><!----><!--]--></aside></div><!--[--><!----><!--]--><div class="theme-hope-content"><h2 id="查询补空值" tabindex="-1"><a class="header-anchor" href="#查询补空值"><span>查询补空值</span></a></h2><p>当对序列进行分段聚合时，某一段时间可能不存在数据，则此段数据的聚合结果为空，但这种空值不利于进行数据可视化展示和分析，需要对空值进行填补。</p><p>查询补空值允许用户按照特定的方法对查询结果填充空值，如取前一个不为空的值，或线性插值。补空值之后的查询结果能更好地反映数据分布，有利于用户进行数据分析。</p><p>在 IoTDB 中，用户可以使用 FILL 子句指定某一时间点或一时间窗口数据缺失的情况下的填充模式。如果查询点空，则填充功能将不起作用。</p><h3 id="填充方法" tabindex="-1"><a class="header-anchor" href="#填充方法"><span>填充方法</span></a></h3><p>IoTDB 目前支持 <code>previous</code> , <code>linear</code>, <code>value</code> 三种空值填充方式，数据类型和支持的填充方法如下表所示：</p><table><thead><tr><th style="text-align:left;">数据类型</th><th style="text-align:left;">支持的填充方法</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><blockquote><p>注意：在 Fill 语句中只能指定一种填充方法。空值填充兼容 0.12 版本及以前的语法（即 fill((&lt;data_type&gt;[&lt;fill_method&gt;(, &lt;before_range&gt;, &lt;after_range&gt;)?])+)），但老的语法也不能同时指定多种填充方式。</p></blockquote><h3 id="单点补空值" tabindex="-1"><a class="header-anchor" href="#单点补空值"><span>单点补空值</span></a></h3><p>当某一特定时间戳的数据为空时，可以使用单值填充对空值进行填充，详细说明如下：</p><h4 id="previous-填充" tabindex="-1"><a class="header-anchor" href="#previous-填充"><span>Previous 填充</span></a></h4><p>当查询的时间戳下数据为空时，将使用前一个时间戳的值来填充空白。 语法定义如下：</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> <span class="token operator">&lt;</span>path<span class="token operator">&gt;</span> <span class="token keyword">from</span> <span class="token operator">&lt;</span>prefixPath<span class="token operator">&gt;</span> <span class="token keyword">where</span> <span class="token keyword">time</span> <span class="token operator">=</span> <span class="token operator">&lt;</span>T<span class="token operator">&gt;</span> fill<span class="token punctuation">(</span>previous<span class="token punctuation">(</span><span class="token punctuation">,</span> <span class="token operator">&lt;</span>before_range<span class="token operator">&gt;</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>下表给出了所有参数的详细说明：</p><table><thead><tr><th style="text-align:left;">参数名称（不区分大小写）</th><th style="text-align:left;">解释</th></tr></thead><tbody><tr><td style="text-align:left;">path, prefixPath</td><td style="text-align:left;">查询路径； 必填项</td></tr><tr><td style="text-align:left;">T</td><td style="text-align:left;">查询时间戳（只能指定一个）； 必填项</td></tr><tr><td style="text-align:left;">before_range</td><td style="text-align:left;">表示前一种方法的有效时间范围。 当 [T-before_range，T] 范围内的值存在时，前一种方法将起作用。 如果未指定 before_range，则 before_range 会使用默认值 default_fill_interval; -1 表示无穷大； 可选字段</td></tr></tbody></table><p>在这里，我们举一个使用 Previous 方法填充空值的示例。 SQL 语句如下：</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> temperature <span class="token keyword">from</span> root<span class="token punctuation">.</span>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">=</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">50.000</span> fill<span class="token punctuation">(</span>previous<span class="token punctuation">,</span> <span class="token number">1</span>m<span class="token punctuation">)</span> 
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>含义：</p><p>由于时间根目录 root.sgcc.wf03.wt01.temperature 在 2017-11-01T16：37：50.000 为空，因此系统使用以前的时间戳 2017-11-01T16：37：00.000（且时间戳位于 [2017-11-01T16:36:50.000, 2017-11-01T16:37:50.000] 范围）进行填充和显示。</p><p>在 <a href="https://github.com/thulab/iotdb/files/4438687/OtherMaterial-Sample.Data.txt" target="_blank" rel="noopener noreferrer">样例数据<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> 中, 该语句的执行结果如下所示：</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|
+-----------------------------+-------------------------------+
|2017-11-01T16:37:50.000+08:00|                          21.93|
+-----------------------------+-------------------------------+
Total line number = 1
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></div><p>值得注意的是，如果在指定的有效时间范围内没有值，系统将不会填充空值，如下所示：</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>IoTDB&gt; select temperature from root.sgcc.wf03.wt01 where time = 2017-11-01T16:37:50.000 fill(previous, 1s) 
+-----------------------------+-------------------------------+
|                         Time|root.sgcc.wf03.wt01.temperature|
+-----------------------------+-------------------------------+
|2017-11-01T16:37:50.000+08:00|                           null|
+-----------------------------+-------------------------------+
Total line number = 1
It costs 0.004s
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><h4 id="linear-填充" tabindex="-1"><a class="header-anchor" href="#linear-填充"><span>Linear 填充</span></a></h4><p>当查询的时间戳下数据为空时，将使用前一个和下一个时间戳的值来填充空白。 语法定义如下：</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> <span class="token operator">&lt;</span>path<span class="token operator">&gt;</span> <span class="token keyword">from</span> <span class="token operator">&lt;</span>prefixPath<span class="token operator">&gt;</span> <span class="token keyword">where</span> <span class="token keyword">time</span> <span class="token operator">=</span> <span class="token operator">&lt;</span>T<span class="token operator">&gt;</span> fill<span class="token punctuation">(</span>linear<span class="token punctuation">(</span><span class="token punctuation">,</span> <span class="token operator">&lt;</span>before_range<span class="token operator">&gt;</span><span class="token punctuation">,</span> <span class="token operator">&lt;</span>after_range<span class="token operator">&gt;</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>下表给出了所有参数的详细说明：</p><table><thead><tr><th style="text-align:left;">参数名称（不区分大小写）</th><th style="text-align:left;">解释</th></tr></thead><tbody><tr><td style="text-align:left;">path, prefixPath</td><td style="text-align:left;">查询路径； 必填项</td></tr><tr><td style="text-align:left;">T</td><td style="text-align:left;">查询时间戳（只能指定一个）； 必填项</td></tr><tr><td style="text-align:left;">before_range, after_range</td><td style="text-align:left;">表示线性方法的有效时间范围。 当 [T - before_range，T + after_range] 范围内的值存在时，前一种方法将起作用。 如果未明确指定 before_range 和 after_range，则使用 default_fill_interval。 -1 表示无穷大； 可选字段</td></tr></tbody></table><p>需要注意的是一旦时间序列在查询时间戳 T 时刻存在有效值，线性填充就会使用这个值作为结果返回。<br> 除此之外，如果在 [T - before_range, T] 或 [T, T + after_range] 两个范围中任意一个范围内不存在有效填充值，则线性填充返回 null 值。</p><p>在这里，我们举一个使用线性方法填充空值的示例。 SQL 语句如下：</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> temperature <span class="token keyword">from</span> root<span class="token punctuation">.</span>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">=</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">50.000</span> fill<span class="token punctuation">(</span>linear<span class="token punctuation">,</span> <span class="token number">1</span>m<span class="token punctuation">,</span> <span class="token number">1</span>m<span class="token punctuation">)</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>含义：</p><p>由于时间根目录 root.sgcc.wf03.wt01.temperature 在 2017-11-01T16:37:50.000 为空，因此系统使用以前的时间戳 2017-11-01T16:37:00.000（且时间戳位于 [2017-11-01T16:36:50.000，2017-11-01T16:37:50.000) 时间范围）及其值 21.927326，下一个时间戳记 2017-11-01T16:38:00.000（且时间戳记位于 (2017-11-01T16:37:50.000, 2017-11-01T16:38:50.000) 时间范围）及其值 25.311783 以执行线性拟合计算：</p><p>21.927326 +（25.311783-21.927326）/ 60s * 50s = 24.747707</p><p>在 <a href="https://github.com/thulab/iotdb/files/4438687/OtherMaterial-Sample.Data.txt" target="_blank" rel="noopener noreferrer">样例数据<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> 中, 该语句的执行结果如下所示：</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|
+-----------------------------+-------------------------------+
|2017-11-01T16:37:50.000+08:00|                      24.747707|
+-----------------------------+-------------------------------+
Total line number = 1
It costs 0.017s
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><h4 id="value-填充" tabindex="-1"><a class="header-anchor" href="#value-填充"><span>Value 填充</span></a></h4><p>当查询的时间戳下数据为空时，将使用给定的值来填充空白。语法定义如下：</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> <span class="token operator">&lt;</span>path<span class="token operator">&gt;</span> <span class="token keyword">from</span> <span class="token operator">&lt;</span>prefixPath<span class="token operator">&gt;</span> <span class="token keyword">where</span> <span class="token keyword">time</span> <span class="token operator">=</span> <span class="token operator">&lt;</span>T<span class="token operator">&gt;</span> fill<span class="token punctuation">(</span>constant<span class="token punctuation">)</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>下表给出了所有参数的详细说明：</p><table><thead><tr><th style="text-align:left;">参数名称（不区分大小写）</th><th style="text-align:left;">解释</th></tr></thead><tbody><tr><td style="text-align:left;">path, prefixPath</td><td style="text-align:left;">查询路径； 必填项</td></tr><tr><td style="text-align:left;">T</td><td style="text-align:left;">查询时间戳（只能指定一个）； 必填项</td></tr><tr><td style="text-align:left;">constant</td><td style="text-align:left;">给定的填充值；必填项</td></tr></tbody></table><p>需要注意的是一旦时间序列在查询时间戳T时刻存在有效值，特定值填充就会使用这个值作为结果返回。</p><p>在这里，我们举一个使用特定值方法填充空值的示例。 SQL语句如下：</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> temperature <span class="token keyword">from</span> root<span class="token punctuation">.</span>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">=</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">50.000</span> fill<span class="token punctuation">(</span><span class="token number">2.0</span><span class="token punctuation">)</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>含义：</p><p>由于时间序列 root.sgcc.wf03.wt01.temperature 在 2017-11-01T16:37:50.000 为空，因此使用给定的值 2.0 进行填充：</p><p>在 <a href="https://github.com/thulab/iotdb/files/4438687/OtherMaterial-Sample.Data.txt" target="_blank" rel="noopener noreferrer">样例数据<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> 中, 该语句的执行结果如下所示：</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|
+-----------------------------+-------------------------------+
|2017-11-01T16:37:50.000+08:00|                           2.0 |
+-----------------------------+-------------------------------+
Total line number = 1
It costs 0.007s
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>在使用 VALUE 方法填充时需要注意，如果查询结果的数据类型与输入常量值不同，IoTDB 将不进行填充</p><p>示例：</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> temperature <span class="token keyword">from</span> root<span class="token punctuation">.</span>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">=</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">50.000</span> fill<span class="token punctuation">(</span><span class="token string">&#39;test&#39;</span><span class="token punctuation">)</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>结果：</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|
+-----------------------------+-------------------------------+
|2017-11-01T16:37:50.000+08:00|                          null |
+-----------------------------+-------------------------------+
Total line number = 1
It costs 0.007s
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><h3 id="降采样补空值" tabindex="-1"><a class="header-anchor" href="#降采样补空值"><span>降采样补空值</span></a></h3><p>IoTDB 支持对原降采样结果进行空值填充，<code>previous</code>、<code>linear</code>、<code>value</code> 填充方式均可作用于查询语句中的任一聚合算子，但一条查询语句只能使用一种空值填充方式。此外，使用时需要注意以下两点：</p><ul><li>在任何情形下都不会填充 <code>count</code> 的聚合结果，因为对于不存在任数据的查询区间，<code>count</code> 的结果为 0。</li><li>分类处理 sum 的聚合结果：若某个查询区间不存在任何数据，sum 的聚合结果为 null，将被 GroupByFill 填充；若某个查询区间内 sum 的聚合结果恰好为 0，那么 GroupByFill 不会填充这个值。</li></ul><p>降采样补空值查询语法同单点补空值查询语法相似，下面列出简单的示例和使用细节：</p><h4 id="previous-和-previousuntillast-的区别" tabindex="-1"><a class="header-anchor" href="#previous-和-previousuntillast-的区别"><span>PREVIOUS 和 PREVIOUSUNTILLAST 的区别</span></a></h4><ul><li>PREVIOUS：只要空值前边有值，就会用其填充空值。</li><li>PREVIOUSUNTILLAST：不会填充此序列最新点后的空值。</li></ul><p>首先检查一下 root.ln.wf01.wt01.temperature 在时间 2017-11-07T23:49:00 以后的值：</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>IoTDB&gt; SELECT temperature FROM root.ln.wf01.wt01 where time &gt;= 2017-11-07T23:49:00
+-----------------------------+-----------------------------+
|                         Time|root.ln.wf01.wt01.temperature|
+-----------------------------+-----------------------------+
|2017-11-07T23:49:00.000+08:00|                         23.7|
|2017-11-07T23:51:00.000+08:00|                        22.24|
|2017-11-07T23:53:00.000+08:00|                        24.58|
|2017-11-07T23:54:00.000+08:00|                        22.52|
|2017-11-07T23:57:00.000+08:00|                        24.39|
|2017-11-08T00:00:00.000+08:00|                        21.07|
+-----------------------------+-----------------------------+
Total line number = 6
It costs 0.010s
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>root.ln.wf01.wt01.temperature 最早时间和值是 2017-11-07T23:49:00 和 23.7；最后时间和值是 2017-11-08T00:00:00 和 21.07</p><p>SQL 示例：</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> last_value<span class="token punctuation">(</span>temperature<span class="token punctuation">)</span> <span class="token keyword">FROM</span> root<span class="token punctuation">.</span>ln<span class="token punctuation">.</span>wf01<span class="token punctuation">.</span>wt01 <span class="token keyword">GROUP</span> <span class="token keyword">BY</span><span class="token punctuation">(</span><span class="token punctuation">[</span><span class="token number">2017</span><span class="token operator">-</span><span class="token number">11</span><span class="token operator">-</span><span class="token number">07</span>T23:<span class="token number">50</span>:<span class="token number">00</span><span class="token punctuation">,</span> <span class="token number">2017</span><span class="token operator">-</span><span class="token number">11</span><span class="token operator">-</span><span class="token number">07</span>T23:<span class="token number">59</span>:<span class="token number">00</span><span class="token punctuation">)</span><span class="token punctuation">,</span><span class="token number">1</span>m<span class="token punctuation">)</span> FILL <span class="token punctuation">(</span>PREVIOUSUNTILLAST<span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token keyword">SELECT</span> last_value<span class="token punctuation">(</span>temperature<span class="token punctuation">)</span> <span class="token keyword">FROM</span> root<span class="token punctuation">.</span>ln<span class="token punctuation">.</span>wf01<span class="token punctuation">.</span>wt01 <span class="token keyword">GROUP</span> <span class="token keyword">BY</span><span class="token punctuation">(</span><span class="token punctuation">[</span><span class="token number">2017</span><span class="token operator">-</span><span class="token number">11</span><span class="token operator">-</span><span class="token number">07</span>T23:<span class="token number">50</span>:<span class="token number">00</span><span class="token punctuation">,</span> <span class="token number">2017</span><span class="token operator">-</span><span class="token number">11</span><span class="token operator">-</span><span class="token number">07</span>T23:<span class="token number">59</span>:<span class="token number">00</span><span class="token punctuation">)</span><span class="token punctuation">,</span><span class="token number">1</span>m<span class="token punctuation">)</span> 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 class="line-number"></div></div></div><p>结果：</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>IoTDB&gt; SELECT last_value(temperature) FROM root.ln.wf01.wt01 GROUP BY([2017-11-07T23:50:00, 2017-11-07T23:59:00),1m) FILL (PREVIOUSUNTILLAST);
+-----------------------------+-----------------------------------------+
|                         Time|last_value(root.ln.wf01.wt01.temperature)|
+-----------------------------+-----------------------------------------+
|2017-11-07T23:50:00.000+08:00|                                     null|
|2017-11-07T23:51:00.000+08:00|                                    22.24|
|2017-11-07T23:52:00.000+08:00|                                    22.24|
|2017-11-07T23:53:00.000+08:00|                                    24.58|
|2017-11-07T23:54:00.000+08:00|                                    22.52|
|2017-11-07T23:55:00.000+08:00|                                    22.52|
|2017-11-07T23:56:00.000+08:00|                                    22.52|
|2017-11-07T23:57:00.000+08:00|                                    24.39|
|2017-11-07T23:58:00.000+08:00|                                     null|
+-----------------------------+-----------------------------------------+
Total line number = 9
It costs 0.007s

IoTDB&gt; SELECT last_value(temperature) FROM root.ln.wf01.wt01 GROUP BY([2017-11-07T23:50:00, 2017-11-07T23:59:00),1m) FILL (PREVIOUS);
+-----------------------------+-----------------------------------------+
|                         Time|last_value(root.ln.wf01.wt01.temperature)|
+-----------------------------+-----------------------------------------+
|2017-11-07T23:50:00.000+08:00|                                     null|
|2017-11-07T23:51:00.000+08:00|                                    22.24|
|2017-11-07T23:52:00.000+08:00|                                    22.24|
|2017-11-07T23:53:00.000+08:00|                                    24.58|
|2017-11-07T23:54:00.000+08:00|                                    22.52|
|2017-11-07T23:55:00.000+08:00|                                    22.52|
|2017-11-07T23:56:00.000+08:00|                                    22.52|
|2017-11-07T23:57:00.000+08:00|                                    24.39|
|2017-11-07T23:58:00.000+08:00|                                    24.39|
+-----------------------------+-----------------------------------------+
Total line number = 9
It costs 0.006s
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="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>解释：</p><p>使用 PREVIOUSUNTILLAST 将不会填充 2017-11-07T23:57:00 以后的值。</p><h4 id="第一个值与最后一个值的填充" tabindex="-1"><a class="header-anchor" href="#第一个值与最后一个值的填充"><span>第一个值与最后一个值的填充</span></a></h4><p>IoTDB 的空值填充方式可以分为 PreviousFill, LinearFill, ValueFill 三大类。其中，PreviousFill 需要知道空值前的第一个非空数据，LinearFill 需要知道空值前后的第一个非空数据才能进行填充。假使某条查询语句返回的结果中第一个或最后一个值为空，就可能导致结果集在首尾存在一段连续的空值，不满足 GroupByFill 的业务期望。</p><p>在上例中，第一个时间区间 [2017-11-07T23:50:00, 2017-11-07T23:51:00) 内没有任何数据，上一个有数据的时间区间是 [2017-11-01T23:49:00, 2017-11-07T23:50:00)，可以通过设置 PREVIOUS 填充向前查询参数 beforeRange 来填充第一个区间的数据，示例如下：</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> last_value<span class="token punctuation">(</span>temperature<span class="token punctuation">)</span> <span class="token keyword">FROM</span> root<span class="token punctuation">.</span>ln<span class="token punctuation">.</span>wf01<span class="token punctuation">.</span>wt01 <span class="token keyword">GROUP</span> <span class="token keyword">BY</span><span class="token punctuation">(</span><span class="token punctuation">[</span><span class="token number">2017</span><span class="token operator">-</span><span class="token number">11</span><span class="token operator">-</span><span class="token number">07</span>T23:<span class="token number">50</span>:<span class="token number">00</span><span class="token punctuation">,</span> <span class="token number">2017</span><span class="token operator">-</span><span class="token number">11</span><span class="token operator">-</span><span class="token number">07</span>T23:<span class="token number">59</span>:<span class="token number">00</span><span class="token punctuation">)</span><span class="token punctuation">,</span><span class="token number">1</span>m<span class="token punctuation">)</span> FILL <span class="token punctuation">(</span>PREVIOUS<span class="token punctuation">,</span> <span class="token number">1</span>m<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>结果：</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>IoTDB&gt; SELECT last_value(temperature) FROM root.ln.wf01.wt01 GROUP BY([2017-11-07T23:50:00, 2017-11-07T23:59:00),1m) FILL (PREVIOUS, 1m);
+-----------------------------+-----------------------------------------+
|                         Time|last_value(root.ln.wf01.wt01.temperature)|
+-----------------------------+-----------------------------------------+
|2017-11-07T23:50:00.000+08:00|                                     23.7|
|2017-11-07T23:51:00.000+08:00|                                    22.24|
|2017-11-07T23:52:00.000+08:00|                                    22.24|
|2017-11-07T23:53:00.000+08:00|                                    24.58|
|2017-11-07T23:54:00.000+08:00|                                    22.52|
|2017-11-07T23:55:00.000+08:00|                                    22.52|
|2017-11-07T23:56:00.000+08:00|                                     null|
|2017-11-07T23:57:00.000+08:00|                                    24.39|
|2017-11-07T23:58:00.000+08:00|                                    24.39|
+-----------------------------+-----------------------------------------+
Total line number = 9
It costs 0.005s
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>解释：</p><p>为了不与原有语义冲突，当不设置 before_range, after_range 参数时，GroupByFill 的空值填充取空值的前一个/后一个非空值完成；当设置 before_range, after_range 参数时，设空值所在记录的时间戳为 t，GroupByFill 取 [t-before_range, t+after_range) 内的前一个/后一个非空值完成填充。</p><p>因为时间区间 [2017-11-07T23:55:00, 2017-11-07T23:57:00) 内均没有数据，所以本例虽然通过设置 before_range 填充了 [2017-11-07T23:50:00, 2017-11-07T23:51:00) 的数据，但由于 before_range 较小，[2017-11-07T23:56:00, 2017-11-07T23:57:00) 的数据无法填充。</p><p>before_range, after_range 参数也可辅助 LINEAR 方式进行填充，示例如下：</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> last_value<span class="token punctuation">(</span>temperature<span class="token punctuation">)</span> <span class="token keyword">FROM</span> root<span class="token punctuation">.</span>ln<span class="token punctuation">.</span>wf01<span class="token punctuation">.</span>wt01 <span class="token keyword">GROUP</span> <span class="token keyword">BY</span><span class="token punctuation">(</span><span class="token punctuation">[</span><span class="token number">2017</span><span class="token operator">-</span><span class="token number">11</span><span class="token operator">-</span><span class="token number">07</span>T23:<span class="token number">50</span>:<span class="token number">00</span><span class="token punctuation">,</span> <span class="token number">2017</span><span class="token operator">-</span><span class="token number">11</span><span class="token operator">-</span><span class="token number">07</span>T23:<span class="token number">59</span>:<span class="token number">00</span><span class="token punctuation">)</span><span class="token punctuation">,</span><span class="token number">1</span>m<span class="token punctuation">)</span> FILL <span class="token punctuation">(</span>LINEAR<span class="token punctuation">,</span> <span class="token number">5</span>m<span class="token punctuation">,</span> <span class="token number">5</span>m<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>结果：</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>IoTDB&gt; SELECT last_value(temperature) FROM root.ln.wf01.wt01 GROUP BY([2017-11-07T23:50:00, 2017-11-07T23:59:00),1m) FILL (LINEAR, 5m, 5m);
+-----------------------------+-----------------------------------------+
|                         Time|last_value(root.ln.wf01.wt01.temperature)|
+-----------------------------+-----------------------------------------+
|2017-11-07T23:50:00.000+08:00|                                22.970001|
|2017-11-07T23:51:00.000+08:00|                                    22.24|
|2017-11-07T23:52:00.000+08:00|                                    23.41|
|2017-11-07T23:53:00.000+08:00|                                    24.58|
|2017-11-07T23:54:00.000+08:00|                                    22.52|
|2017-11-07T23:55:00.000+08:00|                                23.143333|
|2017-11-07T23:56:00.000+08:00|                                23.766666|
|2017-11-07T23:57:00.000+08:00|                                    24.39|
|2017-11-07T23:58:00.000+08:00|                                23.283333|
+-----------------------------+-----------------------------------------+
Total line number = 9
It costs 0.008s
</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><blockquote><p>注意：设原始降采样查询区间为 [start_time, end_time)，在指定 before_range, after_range 参数后，降采样查询结果不变，但查询区间将转变为 [start_time - before_range, end_time + after_range)。因此这两个参数设置较大时会影响效率，使用时需注意。</p></blockquote><h4 id="value-填充-1" tabindex="-1"><a class="header-anchor" href="#value-填充-1"><span>Value 填充</span></a></h4><p>值填充方式会将输入的常量值解析为字符串，填充时尝试将字符串常量转换为对应类型的数据，若转换成功则进行填充，否则就不填充。举例如下：</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> last_value<span class="token punctuation">(</span>temperature<span class="token punctuation">)</span> <span class="token keyword">FROM</span> root<span class="token punctuation">.</span>ln<span class="token punctuation">.</span>wf01<span class="token punctuation">.</span>wt01 <span class="token keyword">GROUP</span> <span class="token keyword">BY</span><span class="token punctuation">(</span><span class="token punctuation">[</span><span class="token number">2017</span><span class="token operator">-</span><span class="token number">11</span><span class="token operator">-</span><span class="token number">07</span>T23:<span class="token number">50</span>:<span class="token number">00</span><span class="token punctuation">,</span> <span class="token number">2017</span><span class="token operator">-</span><span class="token number">11</span><span class="token operator">-</span><span class="token number">07</span>T23:<span class="token number">59</span>:<span class="token number">00</span><span class="token punctuation">)</span><span class="token punctuation">,</span><span class="token number">1</span>m<span class="token punctuation">)</span> FILL <span class="token punctuation">(</span><span class="token number">20.0</span><span class="token punctuation">)</span>
<span class="token keyword">SELECT</span> last_value<span class="token punctuation">(</span>temperature<span class="token punctuation">)</span> <span class="token keyword">FROM</span> root<span class="token punctuation">.</span>ln<span class="token punctuation">.</span>wf01<span class="token punctuation">.</span>wt01 <span class="token keyword">GROUP</span> <span class="token keyword">BY</span><span class="token punctuation">(</span><span class="token punctuation">[</span><span class="token number">2017</span><span class="token operator">-</span><span class="token number">11</span><span class="token operator">-</span><span class="token number">07</span>T23:<span class="token number">50</span>:<span class="token number">00</span><span class="token punctuation">,</span> <span class="token number">2017</span><span class="token operator">-</span><span class="token number">11</span><span class="token operator">-</span><span class="token number">07</span>T23:<span class="token number">59</span>:<span class="token number">00</span><span class="token punctuation">)</span><span class="token punctuation">,</span><span class="token number">1</span>m<span class="token punctuation">)</span> FILL <span class="token punctuation">(</span><span class="token string">&#39;temperature&#39;</span><span class="token punctuation">)</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div></div></div><p>结果：</p><div class="language-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><code>IoTDB&gt; SELECT last_value(temperature) FROM root.ln.wf01.wt01 GROUP BY([2017-11-07T23:50:00, 2017-11-07T23:59:00),1m) FILL (20.0);
+-----------------------------+-----------------------------------------+
|                         Time|last_value(root.ln.wf01.wt01.temperature)|
+-----------------------------+-----------------------------------------+
|2017-11-07T23:50:00.000+08:00|                                     20.0|
|2017-11-07T23:51:00.000+08:00|                                    22.24|
|2017-11-07T23:52:00.000+08:00|                                     20.0|
|2017-11-07T23:53:00.000+08:00|                                    24.58|
|2017-11-07T23:54:00.000+08:00|                                    22.52|
|2017-11-07T23:55:00.000+08:00|                                     20.0|
|2017-11-07T23:56:00.000+08:00|                                     20.0|
|2017-11-07T23:57:00.000+08:00|                                    24.39|
|2017-11-07T23:58:00.000+08:00|                                     20.0|
+-----------------------------+-----------------------------------------+
Total line number = 9
It costs 0.007s

IoTDB&gt; SELECT last_value(temperature) FROM root.ln.wf01.wt01 GROUP BY([2017-11-07T23:50:00, 2017-11-07T23:59:00),1m) FILL (&#39;temperature&#39;);
+-----------------------------+-----------------------------------------+
|                         Time|last_value(root.ln.wf01.wt01.temperature)|
+-----------------------------+-----------------------------------------+
|2017-11-07T23:50:00.000+08:00|                                     null|
|2017-11-07T23:51:00.000+08:00|                                    22.24|
|2017-11-07T23:52:00.000+08:00|                                     null|
|2017-11-07T23:53:00.000+08:00|                                    24.58|
|2017-11-07T23:54:00.000+08:00|                                    22.52|
|2017-11-07T23:55:00.000+08:00|                                     null|
|2017-11-07T23:56:00.000+08:00|                                     null|
|2017-11-07T23:57:00.000+08:00|                                    24.39|
|2017-11-07T23:58:00.000+08:00|                                     null|
+-----------------------------+-----------------------------------------+
Total line number = 9
It costs 0.005s
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="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/zh/UserGuide/V0.13.x/Query-Data/Fill-Null-Value.md" rel="noopener noreferrer" target="_blank" aria-label="发现错误？在 GitHub 上编辑此页" 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><!--]-->发现错误？在 GitHub 上编辑此页<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">上次编辑于: </span><!----></div><!----></div></footer><nav class="vp-page-nav"><a class="route-link nav-link prev" href="/zh/UserGuide/V0.13.x/Query-Data/Last-Query.html" aria-label="最新点查询"><div class="hint"><span class="arrow start"></span>上一页</div><div class="link"><!---->最新点查询</div></a><a class="route-link nav-link next" href="/zh/UserGuide/V0.13.x/Query-Data/Without-Null.html" aria-label="空值过滤"><div class="hint">下一页<span class="arrow end"></span></div><div class="link">空值过滤<!----></div></a></nav><!----><!--[--><!----><!--]--><!--]--></main><!--]--><footer style="padding-bottom:2rem;"><span id="doc-version" style="display:none;">rel/0.13</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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