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aria-label="区间查询"><!---->区间查询<!----></a></li><li><a class="route-link nav-link vp-sidebar-link vp-sidebar-page" href="/zh/UserGuide/V1.1.x/Operators-Functions/Variation-Trend.html" aria-label="趋势计算"><!---->趋势计算<!----></a></li><li><a class="route-link nav-link vp-sidebar-link vp-sidebar-page" href="/zh/UserGuide/V1.1.x/Operators-Functions/Sample.html" aria-label="采样函数"><!---->采样函数<!----></a></li><li><a class="route-link nav-link vp-sidebar-link vp-sidebar-page" href="/zh/UserGuide/V1.1.x/Operators-Functions/Time-Series.html" aria-label="时间序列处理"><!---->时间序列处理<!----></a></li><li><a class="route-link nav-link vp-sidebar-link vp-sidebar-page" href="/zh/UserGuide/V1.1.x/Operators-Functions/Lambda.html" aria-label="Lambda 表达式"><!---->Lambda 表达式<!----></a></li><li><a class="route-link nav-link vp-sidebar-link vp-sidebar-page" href="/zh/UserGuide/V1.1.x/Operators-Functions/Data-Profiling.html" aria-label="数据画像"><!---->数据画像<!----></a></li><li><a class="route-link nav-link vp-sidebar-link 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class="vp-toc-header">此页内容<button type="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 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 level3" href="#选择函数">选择函数</a></li><!----><!--]--></ul><div class="vp-toc-marker" style="top:-1.7rem;"></div></div><!--[--><!----><!--]--></aside></div><!--[--><!----><!--]--><div class="theme-hope-content"><h3 id="选择函数" tabindex="-1"><a class="header-anchor" href="#选择函数"><span>选择函数</span></a></h3><p>目前 IoTDB 支持如下选择函数：</p><table><thead><tr><th>函数名</th><th>输入序列类型</th><th>必要的属性参数</th><th>输出序列类型</th><th>功能描述</th></tr></thead><tbody><tr><td>TOP_K</td><td>INT32 / INT64 / FLOAT / DOUBLE / TEXT</td><td><code>k</code>: 最多选择的数据点数，必须大于 0 小于等于 1000</td><td>与输入序列的实际类型一致</td><td>返回某时间序列中值最大的<code>k</code>个数据点。若多于<code>k</code>个数据点的值并列最大，则返回时间戳最小的数据点。</td></tr><tr><td>BOTTOM_K</td><td>INT32 / INT64 / FLOAT / DOUBLE / TEXT</td><td><code>k</code>: 最多选择的数据点数，必须大于 0 小于等于 1000</td><td>与输入序列的实际类型一致</td><td>返回某时间序列中值最小的<code>k</code>个数据点。若多于<code>k</code>个数据点的值并列最小，则返回时间戳最小的数据点。</td></tr></tbody></table><p>例如：</p><div class="language-sql line-numbers-mode" data-ext="sql" data-title="sql"><pre class="language-sql"><code><span class="token keyword">select</span> s1<span class="token punctuation">,</span> top_k<span class="token punctuation">(</span>s1<span class="token punctuation">,</span> <span class="token string">&#39;k&#39;</span><span class="token operator">=</span><span class="token string">&#39;2&#39;</span><span class="token punctuation">)</span><span class="token punctuation">,</span> bottom_k<span class="token punctuation">(</span>s1<span class="token punctuation">,</span> <span class="token string">&#39;k&#39;</span><span class="token operator">=</span><span class="token string">&#39;2&#39;</span><span class="token punctuation">)</span> <span class="token keyword">from</span> root<span class="token punctuation">.</span>sg1<span class="token punctuation">.</span>d2 <span class="token keyword">where</span> <span class="token keyword">time</span> <span class="token operator">&gt;</span> <span class="token number">2020</span><span class="token operator">-</span><span class="token number">12</span><span class="token operator">-</span><span class="token number">10</span>T20:<span class="token number">36</span>:<span class="token number">15.530</span><span class="token operator">+</span><span class="token number">08</span>:<span class="token number">00</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.sg1.d2.s1|top_k(root.sg1.d2.s1, &quot;k&quot;=&quot;2&quot;)|bottom_k(root.sg1.d2.s1, &quot;k&quot;=&quot;2&quot;)|
+-----------------------------+--------------------+------------------------------+---------------------------------+
|2020-12-10T20:36:15.531+08:00| 1531604122307244742|           1531604122307244742|                             null|
|2020-12-10T20:36:15.532+08:00|-7426070874923281101|                          null|                             null|
|2020-12-10T20:36:15.533+08:00|-7162825364312197604|          -7162825364312197604|                             null|
|2020-12-10T20:36:15.534+08:00|-8581625725655917595|                          null|             -8581625725655917595|
|2020-12-10T20:36:15.535+08:00|-7667364751255535391|                          null|             -7667364751255535391|
+-----------------------------+--------------------+------------------------------+---------------------------------+
Total line number = 5
It costs 0.006s
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