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href="/zh/UserGuide/V1.0.x/Query-Data/Overview.html" class="nav-link sidebar-link sidebar-page" aria-label="概述"><!---->概述<!----></a><ul class="sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a aria-current="page" href="/zh/UserGuide/V1.0.x/Query-Data/Select-Expression.html" class="router-link-active router-link-exact-active nav-link active sidebar-link sidebar-page active" aria-label="选择表达式"><!---->选择表达式<!----></a><ul class="sidebar-sub-headers"><li class="sidebar-sub-header"><a aria-current="page" href="/zh/UserGuide/V1.0.x/Query-Data/Select-Expression.html#使用别名" class="router-link-active router-link-exact-active nav-link sidebar-link heading" aria-label="使用别名"><!---->使用别名<!----></a><ul class="sidebar-sub-headers"></ul></li><li class="sidebar-sub-header"><a aria-current="page" href="/zh/UserGuide/V1.0.x/Query-Data/Select-Expression.html#运算符" class="router-link-active router-link-exact-active nav-link sidebar-link heading" aria-label="运算符"><!---->运算符<!----></a><ul class="sidebar-sub-headers"></ul></li><li class="sidebar-sub-header"><a aria-current="page" href="/zh/UserGuide/V1.0.x/Query-Data/Select-Expression.html#函数" class="router-link-active router-link-exact-active nav-link sidebar-link heading" aria-label="函数"><!---->函数<!----></a><ul class="sidebar-sub-headers"><li class="sidebar-sub-header"><a aria-current="page" href="/zh/UserGuide/V1.0.x/Query-Data/Select-Expression.html#聚合函数" class="router-link-active router-link-exact-active nav-link sidebar-link heading" aria-label="聚合函数"><!---->聚合函数<!----></a><ul class="sidebar-sub-headers"></ul></li><li class="sidebar-sub-header"><a aria-current="page" href="/zh/UserGuide/V1.0.x/Query-Data/Select-Expression.html#时间序列生成函数" class="router-link-active router-link-exact-active nav-link sidebar-link heading" aria-label="时间序列生成函数"><!---->时间序列生成函数<!----></a><ul class="sidebar-sub-headers"></ul></li></ul></li><li class="sidebar-sub-header"><a aria-current="page" href="/zh/UserGuide/V1.0.x/Query-Data/Select-Expression.html#嵌套表达式举例" class="router-link-active router-link-exact-active nav-link sidebar-link heading" aria-label="嵌套表达式举例"><!---->嵌套表达式举例<!----></a><ul class="sidebar-sub-headers"><li class="sidebar-sub-header"><a aria-current="page" href="/zh/UserGuide/V1.0.x/Query-Data/Select-Expression.html#时间序列查询嵌套表达式" class="router-link-active router-link-exact-active nav-link sidebar-link heading" aria-label="时间序列查询嵌套表达式"><!---->时间序列查询嵌套表达式<!----></a><ul class="sidebar-sub-headers"></ul></li><li class="sidebar-sub-header"><a aria-current="page" href="/zh/UserGuide/V1.0.x/Query-Data/Select-Expression.html#聚合查询嵌套表达式" class="router-link-active router-link-exact-active nav-link sidebar-link heading" aria-label="聚合查询嵌套表达式"><!---->聚合查询嵌套表达式<!----></a><ul class="sidebar-sub-headers"></ul></li></ul></li></ul><!--]--></li><li><!--[--><a href="/zh/UserGuide/V1.0.x/Query-Data/Last-Query.html" class="nav-link sidebar-link sidebar-page" aria-label="最新点查询"><!---->最新点查询<!----></a><ul class="sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a href="/zh/UserGuide/V1.0.x/Query-Data/Align-By.html" class="nav-link sidebar-link sidebar-page" aria-label="查询对齐模式"><!---->查询对齐模式<!----></a><ul class="sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a href="/zh/UserGuide/V1.0.x/Query-Data/Where-Condition.html" class="nav-link sidebar-link sidebar-page" aria-label="查询过滤条件"><!---->查询过滤条件<!----></a><ul class="sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a href="/zh/UserGuide/V1.0.x/Query-Data/Group-By.html" class="nav-link sidebar-link sidebar-page" aria-label="分段分组聚合"><!---->分段分组聚合<!----></a><ul class="sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a href="/zh/UserGuide/V1.0.x/Query-Data/Having-Condition.html" class="nav-link sidebar-link sidebar-page" aria-label="聚合结果过滤"><!---->聚合结果过滤<!----></a><ul class="sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a href="/zh/UserGuide/V1.0.x/Query-Data/Fill.html" class="nav-link sidebar-link sidebar-page" aria-label="结果集补空值"><!---->结果集补空值<!----></a><ul class="sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a href="/zh/UserGuide/V1.0.x/Query-Data/Pagination.html" class="nav-link sidebar-link sidebar-page" aria-label="结果集分页"><!---->结果集分页<!----></a><ul class="sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a href="/zh/UserGuide/V1.0.x/Query-Data/Select-Into.html" class="nav-link sidebar-link sidebar-page" aria-label="查询写回"><!---->查询写回<!----></a><ul class="sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a href="/zh/UserGuide/V1.0.x/Query-Data/Continuous-Query.html" class="nav-link sidebar-link sidebar-page" aria-label="连续查询"><!---->连续查询<!----></a><ul class="sidebar-sub-headers"></ul><!--]--></li></ul></section></li><li><section class="sidebar-group"><button class="sidebar-heading clickable"><!----><span class="title">运算符和函数</span><span class="arrow end"></span></button><!----></section></li><li><section class="sidebar-group"><button class="sidebar-heading clickable"><!----><span class="title">触发器</span><span class="arrow end"></span></button><!----></section></li><li><section class="sidebar-group"><button class="sidebar-heading clickable"><!----><span class="title">监控告警</span><span class="arrow end"></span></button><!----></section></li><li><section class="sidebar-group"><button class="sidebar-heading clickable"><!----><span class="title">权限管理</span><span class="arrow end"></span></button><!----></section></li><li><section class="sidebar-group"><button class="sidebar-heading clickable"><!----><span class="title">运维工具</span><span class="arrow end"></span></button><!----></section></li><li><section class="sidebar-group"><button class="sidebar-heading clickable"><!----><span class="title">端云协同</span><span class="arrow end"></span></button><!----></section></li><li><section class="sidebar-group"><button class="sidebar-heading clickable"><!----><span class="title">系统集成</span><span class="arrow end"></span></button><!----></section></li><li><section class="sidebar-group"><button class="sidebar-heading clickable"><!----><span class="title">分布式</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">参考</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><!---->选择表达式</h1><div class="page-info"><!----><!----><!----><!----><span class="page-reading-time-info" aria-label="阅读时间"><svg xmlns="http://www.w3.org/2000/svg" class="icon timer-icon" viewBox="0 0 1024 1024" fill="currentColor" aria-label="timer icon"><path 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id="toc"><!--[--><!----><!--]--><div class="toc-header">此页内容<button class="print-button" title="打印"><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="/zh/UserGuide/V1.0.x/Query-Data/Select-Expression.html#使用别名" class="router-link-active router-link-exact-active toc-link level2">使用别名</a></li><!----><!--]--><!--[--><li class="toc-item"><a aria-current="page" href="/zh/UserGuide/V1.0.x/Query-Data/Select-Expression.html#运算符" class="router-link-active router-link-exact-active toc-link level2">运算符</a></li><!----><!--]--><!--[--><li class="toc-item"><a aria-current="page" href="/zh/UserGuide/V1.0.x/Query-Data/Select-Expression.html#函数" class="router-link-active router-link-exact-active toc-link level2">函数</a></li><ul class="toc-list"><!--[--><li class="toc-item"><a aria-current="page" href="/zh/UserGuide/V1.0.x/Query-Data/Select-Expression.html#聚合函数" class="router-link-active router-link-exact-active toc-link level3">聚合函数</a></li><!----><!--]--><!--[--><li class="toc-item"><a aria-current="page" href="/zh/UserGuide/V1.0.x/Query-Data/Select-Expression.html#时间序列生成函数" class="router-link-active router-link-exact-active toc-link level3">时间序列生成函数</a></li><!----><!--]--></ul><!--]--><!--[--><li class="toc-item"><a aria-current="page" href="/zh/UserGuide/V1.0.x/Query-Data/Select-Expression.html#嵌套表达式举例" class="router-link-active router-link-exact-active toc-link level2">嵌套表达式举例</a></li><ul class="toc-list"><!--[--><li class="toc-item"><a aria-current="page" href="/zh/UserGuide/V1.0.x/Query-Data/Select-Expression.html#时间序列查询嵌套表达式" class="router-link-active router-link-exact-active toc-link level3">时间序列查询嵌套表达式</a></li><!----><!--]--><!--[--><li class="toc-item"><a aria-current="page" href="/zh/UserGuide/V1.0.x/Query-Data/Select-Expression.html#聚合查询嵌套表达式" class="router-link-active router-link-exact-active toc-link level3">聚合查询嵌套表达式</a></li><!----><!--]--></ul><!--]--></ul></div><!--[--><!----><!--]--></aside></div><!----><div class="theme-hope-content"><!--

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--><h1 id="选择表达式" tabindex="-1"><a class="header-anchor" href="#选择表达式" aria-hidden="true">#</a> 选择表达式</h1><p><code>SELECT</code> 子句指定查询的输出，由若干个 <code>selectExpr</code> 组成。 每个 <code>selectExpr</code> 定义了查询结果中的一列或多列。</p><p><strong><code>selectExpr</code> 是一个由时间序列路径后缀、常量、函数和运算符组成的表达式。即 <code>selectExpr</code> 中可以包含：</strong></p><ul><li>时间序列路径后缀（支持使用通配符）</li><li>运算符 <ul><li>算数运算符</li><li>比较运算符</li><li>逻辑运算符</li></ul></li><li>函数 <ul><li>聚合函数</li><li>时间序列生成函数（包括内置函数和用户自定义函数）</li></ul></li><li>常量</li></ul><h2 id="使用别名" tabindex="-1"><a class="header-anchor" href="#使用别名" aria-hidden="true">#</a> 使用别名</h2><p>由于 IoTDB 独特的数据模型，在每个传感器前都附带有设备等诸多额外信息。有时，我们只针对某个具体设备查询，而这些前缀信息频繁显示造成了冗余，影响了结果集的显示与分析。</p><p>IoTDB 支持使用<code>AS</code>为查询结果集中的列指定别名。</p><p><strong>示例：</strong></p><div class="language-sql line-numbers-mode" data-ext="sql"><pre class="language-sql"><code><span class="token keyword">select</span> s1 <span class="token keyword">as</span> temperature<span class="token punctuation">,</span> s2 <span class="token keyword">as</span> speed <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 punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>结果集将显示为：</p><table><thead><tr><th>Time</th><th>temperature</th><th>speed</th></tr></thead><tbody><tr><td>...</td><td>...</td><td>...</td></tr></tbody></table><h2 id="运算符" tabindex="-1"><a class="header-anchor" href="#运算符" aria-hidden="true">#</a> 运算符</h2><p>IoTDB 中支持的运算符列表见文档 <a href="/zh/UserGuide/V1.0.x/Operators-Functions/Overview.html" class="">运算符和函数</a>。</p><h2 id="函数" tabindex="-1"><a class="header-anchor" href="#函数" aria-hidden="true">#</a> 函数</h2><h3 id="聚合函数" tabindex="-1"><a class="header-anchor" href="#聚合函数" aria-hidden="true">#</a> 聚合函数</h3><p>聚合函数是多对一函数。它们对一组值进行聚合计算，得到单个聚合结果。</p><p><strong>包含聚合函数的查询称为聚合查询</strong>，否则称为时间序列查询。</p><p><strong>注意：聚合查询和时间序列查询不能混合使用。</strong> 下列语句是不支持的：</p><div class="language-sql line-numbers-mode" data-ext="sql"><pre class="language-sql"><code><span class="token keyword">select</span> s1<span class="token punctuation">,</span> <span class="token function">count</span><span class="token punctuation">(</span>s1<span class="token punctuation">)</span> <span class="token keyword">from</span> root<span class="token punctuation">.</span>sg<span class="token punctuation">.</span>d1<span class="token punctuation">;</span>
<span class="token keyword">select</span> sin<span class="token punctuation">(</span>s1<span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token function">count</span><span class="token punctuation">(</span>s1<span class="token punctuation">)</span> <span class="token keyword">from</span> root<span class="token punctuation">.</span>sg<span class="token punctuation">.</span>d1<span class="token punctuation">;</span>
<span class="token keyword">select</span> s1<span class="token punctuation">,</span> <span class="token function">count</span><span class="token punctuation">(</span>s1<span class="token punctuation">)</span> <span class="token keyword">from</span> root<span class="token punctuation">.</span>sg<span class="token punctuation">.</span>d1 <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">10</span><span class="token punctuation">,</span><span class="token number">100</span><span class="token punctuation">)</span><span class="token punctuation">,</span><span class="token number">10</span>ms<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></div><p>IoTDB 支持的聚合函数见文档 <a href="/zh/UserGuide/V1.0.x/Operators-Functions/Aggregation.html" class="">聚合函数</a>。</p><h3 id="时间序列生成函数" tabindex="-1"><a class="header-anchor" href="#时间序列生成函数" aria-hidden="true">#</a> 时间序列生成函数</h3><p>时间序列生成函数接受若干原始时间序列作为输入，产生一列时间序列输出。与聚合函数不同的是，时间序列生成函数的结果集带有时间戳列。</p><p>所有的时间序列生成函数都可以接受 * 作为输入，都可以与原始时间序列查询混合进行。</p><h4 id="内置时间序列生成函数" tabindex="-1"><a class="header-anchor" href="#内置时间序列生成函数" aria-hidden="true">#</a> 内置时间序列生成函数</h4><p>IoTDB 中支持的内置函数列表见文档 <a href="/zh/UserGuide/V1.0.x/Operators-Functions/Overview.html" class="">运算符和函数</a>。</p><h4 id="自定义时间序列生成函数" tabindex="-1"><a class="header-anchor" href="#自定义时间序列生成函数" aria-hidden="true">#</a> 自定义时间序列生成函数</h4><p>IoTDB 支持支持通过用户自定义函数（点击查看： <a href="/zh/UserGuide/V1.0.x/Operators-Functions/User-Defined-Function.html" class="">用户自定义函数</a> ） 能力进行函数功能扩展。</p><h2 id="嵌套表达式举例" tabindex="-1"><a class="header-anchor" href="#嵌套表达式举例" aria-hidden="true">#</a> 嵌套表达式举例</h2><p>IoTDB 支持嵌套表达式，由于聚合查询和时间序列查询不能在一条查询语句中同时出现，我们将支持的嵌套表达式分为时间序列查询嵌套表达式和聚合查询嵌套表达式两类。</p><h3 id="时间序列查询嵌套表达式" tabindex="-1"><a class="header-anchor" href="#时间序列查询嵌套表达式" aria-hidden="true">#</a> 时间序列查询嵌套表达式</h3><p>IoTDB 支持在 <code>SELECT</code> 子句中计算由<strong>时间序列、常量、时间序列生成函数（包括用户自定义函数）和运算符</strong>组成的任意嵌套表达式。</p><p><strong>说明：</strong></p><ul><li>当某个时间戳下左操作数和右操作数都不为空（<code>null</code>）时，表达式才会有结果，否则表达式值为<code>null</code>，且默认不出现在结果集中。</li><li>如果表达式中某个操作数对应多条时间序列（如通配符 <code>*</code>），那么每条时间序列对应的结果都会出现在结果集中（按照笛卡尔积形式）。</li></ul><p><strong>示例 1：</strong></p><div class="language-sql line-numbers-mode" data-ext="sql"><pre class="language-sql"><code><span class="token keyword">select</span> a<span class="token punctuation">,</span>
       b<span class="token punctuation">,</span>
       <span class="token punctuation">(</span><span class="token punctuation">(</span>a <span class="token operator">+</span> <span class="token number">1</span><span class="token punctuation">)</span> <span class="token operator">*</span> <span class="token number">2</span> <span class="token operator">-</span> <span class="token number">1</span><span class="token punctuation">)</span> <span class="token operator">%</span> <span class="token number">2</span> <span class="token operator">+</span> <span class="token number">1.5</span><span class="token punctuation">,</span>
       sin<span class="token punctuation">(</span>a <span class="token operator">+</span> sin<span class="token punctuation">(</span>a <span class="token operator">+</span> sin<span class="token punctuation">(</span>b<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><span class="token punctuation">(</span>a <span class="token operator">+</span> b<span class="token punctuation">)</span> <span class="token operator">*</span> <span class="token punctuation">(</span>sin<span class="token punctuation">(</span>a <span class="token operator">+</span> b<span class="token punctuation">)</span> <span class="token operator">*</span> sin<span class="token punctuation">(</span>a <span class="token operator">+</span> b<span class="token punctuation">)</span> <span class="token operator">+</span> cos<span class="token punctuation">(</span>a <span class="token operator">+</span> b<span class="token punctuation">)</span> <span class="token operator">*</span> cos<span class="token punctuation">(</span>a <span class="token operator">+</span> b<span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token operator">+</span> <span class="token number">1</span>
<span class="token keyword">from</span> root<span class="token punctuation">.</span>sg1<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></div><p>运行结果：</p><div class="language-text line-numbers-mode" data-ext="text"><pre class="language-text"><code>+-----------------------------+----------+----------+----------------------------------------+---------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------------------------------+
|                         Time|root.sg1.a|root.sg1.b|((((root.sg1.a + 1) * 2) - 1) % 2) + 1.5|sin(root.sg1.a + sin(root.sg1.a + sin(root.sg1.b)))|(-root.sg1.a + root.sg1.b * ((sin(root.sg1.a + root.sg1.b) * sin(root.sg1.a + root.sg1.b)) + (cos(root.sg1.a + root.sg1.b) * cos(root.sg1.a + root.sg1.b)))) + 1|
+-----------------------------+----------+----------+----------------------------------------+---------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------------------------------+
|1970-01-01T08:00:00.010+08:00|         1|         1|                                     2.5|                                 0.9238430524420609|                                                                                                                      -1.0|
|1970-01-01T08:00:00.020+08:00|         2|         2|                                     2.5|                                 0.7903505371876317|                                                                                                                      -3.0|
|1970-01-01T08:00:00.030+08:00|         3|         3|                                     2.5|                                0.14065207680386618|                                                                                                                      -5.0|
|1970-01-01T08:00:00.040+08:00|         4|      null|                                     2.5|                                               null|                                                                                                                      null|
|1970-01-01T08:00:00.050+08:00|      null|         5|                                    null|                                               null|                                                                                                                      null|
|1970-01-01T08:00:00.060+08:00|         6|         6|                                     2.5|                                -0.7288037411970916|                                                                                                                     -11.0|
+-----------------------------+----------+----------+----------------------------------------+---------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------------------------------+
Total line number = 6
It costs 0.048s
</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><strong>示例 2：</strong></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>a <span class="token operator">+</span> b<span class="token punctuation">)</span> <span class="token operator">*</span> <span class="token number">2</span> <span class="token operator">+</span> sin<span class="token punctuation">(</span>a<span class="token punctuation">)</span> <span class="token keyword">from</span> root<span class="token punctuation">.</span>sg
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>运行结果：</p><div class="language-text line-numbers-mode" data-ext="text"><pre class="language-text"><code>+-----------------------------+----------------------------------------------+
|                         Time|((root.sg.a + root.sg.b) * 2) + sin(root.sg.a)|
+-----------------------------+----------------------------------------------+
|1970-01-01T08:00:00.010+08:00|                             59.45597888911063|
|1970-01-01T08:00:00.020+08:00|                            100.91294525072763|
|1970-01-01T08:00:00.030+08:00|                            139.01196837590714|
|1970-01-01T08:00:00.040+08:00|                            180.74511316047935|
|1970-01-01T08:00:00.050+08:00|                            219.73762514629607|
|1970-01-01T08:00:00.060+08:00|                             259.6951893788978|
|1970-01-01T08:00:00.070+08:00|                             300.7738906815579|
|1970-01-01T08:00:00.090+08:00|                             39.45597888911063|
|1970-01-01T08:00:00.100+08:00|                             39.45597888911063|
+-----------------------------+----------------------------------------------+
Total line number = 9
It costs 0.011s
</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><p><strong>示例 3：</strong></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>a <span class="token operator">+</span> <span class="token operator">*</span><span class="token punctuation">)</span> <span class="token operator">/</span> <span class="token number">2</span>  <span class="token keyword">from</span> root<span class="token punctuation">.</span>sg1
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>运行结果：</p><div class="language-text line-numbers-mode" data-ext="text"><pre class="language-text"><code>+-----------------------------+-----------------------------+-----------------------------+
|                         Time|(root.sg1.a + root.sg1.a) / 2|(root.sg1.a + root.sg1.b) / 2|
+-----------------------------+-----------------------------+-----------------------------+
|1970-01-01T08:00:00.010+08:00|                          1.0|                          1.0|
|1970-01-01T08:00:00.020+08:00|                          2.0|                          2.0|
|1970-01-01T08:00:00.030+08:00|                          3.0|                          3.0|
|1970-01-01T08:00:00.040+08:00|                          4.0|                         null|
|1970-01-01T08:00:00.060+08:00|                          6.0|                          6.0|
+-----------------------------+-----------------------------+-----------------------------+
Total line number = 5
It costs 0.011s
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p><strong>示例 4：</strong></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>a <span class="token operator">+</span> b<span class="token punctuation">)</span> <span class="token operator">*</span> <span class="token number">3</span> <span class="token keyword">from</span> root<span class="token punctuation">.</span>sg<span class="token punctuation">,</span> root<span class="token punctuation">.</span>ln
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>运行结果：</p><div class="language-text line-numbers-mode" data-ext="text"><pre class="language-text"><code>+-----------------------------+---------------------------+---------------------------+---------------------------+---------------------------+
|                         Time|(root.sg.a + root.sg.b) * 3|(root.sg.a + root.ln.b) * 3|(root.ln.a + root.sg.b) * 3|(root.ln.a + root.ln.b) * 3|
+-----------------------------+---------------------------+---------------------------+---------------------------+---------------------------+
|1970-01-01T08:00:00.010+08:00|                       90.0|                      270.0|                      360.0|                      540.0|
|1970-01-01T08:00:00.020+08:00|                      150.0|                      330.0|                      690.0|                      870.0|
|1970-01-01T08:00:00.030+08:00|                      210.0|                      450.0|                      570.0|                      810.0|
|1970-01-01T08:00:00.040+08:00|                      270.0|                      240.0|                      690.0|                      660.0|
|1970-01-01T08:00:00.050+08:00|                      330.0|                       null|                       null|                       null|
|1970-01-01T08:00:00.060+08:00|                      390.0|                       null|                       null|                       null|
|1970-01-01T08:00:00.070+08:00|                      450.0|                       null|                       null|                       null|
|1970-01-01T08:00:00.090+08:00|                       60.0|                       null|                       null|                       null|
|1970-01-01T08:00:00.100+08:00|                       60.0|                       null|                       null|                       null|
+-----------------------------+---------------------------+---------------------------+---------------------------+---------------------------+
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="聚合查询嵌套表达式" tabindex="-1"><a class="header-anchor" href="#聚合查询嵌套表达式" aria-hidden="true">#</a> 聚合查询嵌套表达式</h3><p>IoTDB 支持在 <code>SELECT</code> 子句中计算由<strong>聚合函数、常量、时间序列生成函数和表达式</strong>组成的任意嵌套表达式。</p><p><strong>说明：</strong></p><ul><li>当某个时间戳下左操作数和右操作数都不为空（<code>null</code>）时，表达式才会有结果，否则表达式值为<code>null</code>，且默认不出现在结果集中。但在使用<code>GROUP BY</code>子句的聚合查询嵌套表达式中，我们希望保留每个时间窗口的值，所以表达式值为<code>null</code>的窗口也包含在结果集中。</li><li>如果表达式中某个操作数对应多条时间序列（如通配符<code>*</code>），那么每条时间序列对应的结果都会出现在结果集中（按照笛卡尔积形式）。</li></ul><p><strong>示例 1：</strong></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 function">avg</span><span class="token punctuation">(</span>temperature<span class="token punctuation">)</span><span class="token punctuation">,</span>
       sin<span class="token punctuation">(</span><span class="token function">avg</span><span class="token punctuation">(</span>temperature<span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">,</span>
       <span class="token function">avg</span><span class="token punctuation">(</span>temperature<span class="token punctuation">)</span> <span class="token operator">+</span> <span class="token number">1</span><span class="token punctuation">,</span>
       <span class="token operator">-</span><span class="token function">sum</span><span class="token punctuation">(</span>hardware<span class="token punctuation">)</span><span class="token punctuation">,</span>
       <span class="token function">avg</span><span class="token punctuation">(</span>temperature<span class="token punctuation">)</span> <span class="token operator">+</span> <span class="token function">sum</span><span class="token punctuation">(</span>hardware<span class="token punctuation">)</span>
<span class="token keyword">from</span> root<span class="token punctuation">.</span>ln<span class="token punctuation">.</span>wf01<span class="token punctuation">.</span>wt01<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></div><p>运行结果：</p><div class="language-text line-numbers-mode" data-ext="text"><pre class="language-text"><code>+----------------------------------+---------------------------------------+--------------------------------------+--------------------------------+--------------------------------------------------------------------+
|avg(root.ln.wf01.wt01.temperature)|sin(avg(root.ln.wf01.wt01.temperature))|avg(root.ln.wf01.wt01.temperature) + 1|-sum(root.ln.wf01.wt01.hardware)|avg(root.ln.wf01.wt01.temperature) + sum(root.ln.wf01.wt01.hardware)|
+----------------------------------+---------------------------------------+--------------------------------------+--------------------------------+--------------------------------------------------------------------+
|                15.927999999999999|                   -0.21826546964855045|                    16.927999999999997|                         -7426.0|                                                            7441.928|
+----------------------------------+---------------------------------------+--------------------------------------+--------------------------------+--------------------------------------------------------------------+
Total line number = 1
It costs 0.009s
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p><strong>示例 2：</strong></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 function">avg</span><span class="token punctuation">(</span><span class="token operator">*</span><span class="token punctuation">)</span><span class="token punctuation">,</span> 
	   <span class="token punctuation">(</span><span class="token function">avg</span><span class="token punctuation">(</span><span class="token operator">*</span><span class="token punctuation">)</span> <span class="token operator">+</span> <span class="token number">1</span><span class="token punctuation">)</span> <span class="token operator">*</span> <span class="token number">3</span> <span class="token operator">/</span> <span class="token number">2</span> <span class="token operator">-</span><span class="token number">1</span> 
<span class="token keyword">from</span> root<span class="token punctuation">.</span>sg1
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>运行结果：</p><div class="language-text line-numbers-mode" data-ext="text"><pre class="language-text"><code>+---------------+---------------+-------------------------------------+-------------------------------------+
|avg(root.sg1.a)|avg(root.sg1.b)|(avg(root.sg1.a) + 1) * 3 / 2 - 1    |(avg(root.sg1.b) + 1) * 3 / 2 - 1    |
+---------------+---------------+-------------------------------------+-------------------------------------+
|            3.2|            3.4|                    5.300000000000001|                   5.6000000000000005|
+---------------+---------------+-------------------------------------+-------------------------------------+
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><strong>示例 3：</strong></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 function">avg</span><span class="token punctuation">(</span>temperature<span class="token punctuation">)</span><span class="token punctuation">,</span>
       sin<span class="token punctuation">(</span><span class="token function">avg</span><span class="token punctuation">(</span>temperature<span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">,</span>
       <span class="token function">avg</span><span class="token punctuation">(</span>temperature<span class="token punctuation">)</span> <span class="token operator">+</span> <span class="token number">1</span><span class="token punctuation">,</span>
       <span class="token operator">-</span><span class="token function">sum</span><span class="token punctuation">(</span>hardware<span class="token punctuation">)</span><span class="token punctuation">,</span>
       <span class="token function">avg</span><span class="token punctuation">(</span>temperature<span class="token punctuation">)</span> <span class="token operator">+</span> <span class="token function">sum</span><span class="token punctuation">(</span>hardware<span class="token punctuation">)</span> <span class="token keyword">as</span> custom_sum
<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">10</span><span class="token punctuation">,</span> <span class="token number">90</span><span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token number">10</span>ms<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></div><p>运行结果：</p><div class="language-text line-numbers-mode" data-ext="text"><pre class="language-text"><code>+-----------------------------+----------------------------------+---------------------------------------+--------------------------------------+--------------------------------+----------+
|                         Time|avg(root.ln.wf01.wt01.temperature)|sin(avg(root.ln.wf01.wt01.temperature))|avg(root.ln.wf01.wt01.temperature) + 1|-sum(root.ln.wf01.wt01.hardware)|custom_sum|
+-----------------------------+----------------------------------+---------------------------------------+--------------------------------------+--------------------------------+----------+
|1970-01-01T08:00:00.010+08:00|                13.987499999999999|                     0.9888207947857667|                    14.987499999999999|                         -3211.0| 3224.9875|
|1970-01-01T08:00:00.020+08:00|                              29.6|                    -0.9701057337071853|                                  30.6|                         -3720.0|    3749.6|
|1970-01-01T08:00:00.030+08:00|                              null|                                   null|                                  null|                            null|      null|
|1970-01-01T08:00:00.040+08:00|                              null|                                   null|                                  null|                            null|      null|
|1970-01-01T08:00:00.050+08:00|                              null|                                   null|                                  null|                            null|      null|
|1970-01-01T08:00:00.060+08:00|                              null|                                   null|                                  null|                            null|      null|
|1970-01-01T08:00:00.070+08:00|                              null|                                   null|                                  null|                            null|      null|
|1970-01-01T08:00:00.080+08:00|                              null|                                   null|                                  null|                            null|      null|
+-----------------------------+----------------------------------+---------------------------------------+--------------------------------------+--------------------------------+----------+
Total line number = 8
It costs 0.012s
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div 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/1.0/docs/zh/UserGuide/Query-Data/Select-Expression.md" rel="noopener noreferrer" target="_blank" aria-label="发现错误？在 GitHub 上编辑此页" 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><!--]-->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="meta-item git-info"><!----><!----></div></footer><nav class="page-nav"><a href="/zh/UserGuide/V1.0.x/Query-Data/Overview.html" class="nav-link prev" aria-label="概述"><div class="hint"><span class="arrow start"></span>上一页</div><div class="link"><!---->概述</div></a><a href="/zh/UserGuide/V1.0.x/Query-Data/Last-Query.html" class="nav-link next" aria-label="最新点查询"><div class="hint">下一页<span class="arrow end"></span></div><div class="link">最新点查询<!----></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 © 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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