| import{_ as n,O as e,P as s,ah as t,aW as a}from"./framework-62ad666a.js";const o={},i=a(`<h3 id="选择函数" tabindex="-1"><a class="header-anchor" href="#选择函数" aria-hidden="true">#</a> 选择函数</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"><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">'k'</span><span class="token operator">=</span><span class="token string">'2'</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">'k'</span><span class="token operator">=</span><span class="token string">'2'</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">></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"><pre class="language-text"><code>+-----------------------------+--------------------+------------------------------+---------------------------------+ |
| | Time| root.sg1.d2.s1|top_k(root.sg1.d2.s1, "k"="2")|bottom_k(root.sg1.d2.s1, "k"="2")| |
| +-----------------------------+--------------------+------------------------------+---------------------------------+ |
| |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 |
| </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>`,7);function c(d,l){return e(),s("div",null,[t(` |
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