| import{_ as e,O as s,P as t,ah as n,aW as d}from"./framework-e4340ccd.js";const i={},r=d(`<h2 id="数据类型转换" tabindex="-1"><a class="header-anchor" href="#数据类型转换" aria-hidden="true">#</a> 数据类型转换</h2><h3 id="cast" tabindex="-1"><a class="header-anchor" href="#cast" aria-hidden="true">#</a> CAST</h3><h4 id="函数简介" tabindex="-1"><a class="header-anchor" href="#函数简介" aria-hidden="true">#</a> 函数简介</h4><p>当前 IoTDB 支持6种数据类型，其中包括 INT32、INT64、FLOAT、DOUBLE、BOOLEAN 以及 TEXT。当我们对数据进行查询或者计算时可能需要进行数据类型的转换， 比如说将 TEXT 转换为 INT32，或者提高数据精度，比如说将 FLOAT 转换为 DOUBLE。IoTDB 支持使用cast 函数对数据类型进行转换。</p><p>语法示例如下：</p><div class="language-sql line-numbers-mode" data-ext="sql"><pre class="language-sql"><code><span class="token keyword">SELECT</span> cast<span class="token punctuation">(</span>s1 <span class="token keyword">as</span> INT32<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>cast 函数语法形式上与 PostgreSQL 一致，AS 后指定的数据类型表明要转换成的目标类型，目前 IoTDB 支持的六种数据类型均可以在 cast 函数中使用，遵循的转换规则如下表所示，其中行表示原始数据类型，列表示要转化成的目标数据类型：</p><table><thead><tr><th></th><th><strong>INT32</strong></th><th><strong>INT64</strong></th><th><strong>FLOAT</strong></th><th><strong>DOUBLE</strong></th><th><strong>BOOLEAN</strong></th><th><strong>TEXT</strong></th></tr></thead><tbody><tr><td><strong>INT32</strong></td><td>不转化</td><td>直接转化</td><td>直接转化</td><td>直接转化</td><td>!=0 : true<br>==0: false</td><td>String.valueOf()</td></tr><tr><td><strong>INT64</strong></td><td>超出 INT32 范围：执行抛异常<br>否则：直接转化</td><td>不转化</td><td>直接转化</td><td>直接转化</td><td>!=0L : true<br>==0: false</td><td>String.valueOf()</td></tr><tr><td><strong>FLOAT</strong></td><td>超出 INT32 范围：执行抛异常<br>否则：四舍五入(Math.round())</td><td>超出 INT64 范围：执行抛异常<br>否则：四舍五入(Math.round())</td><td>不转化</td><td>直接转化</td><td>!=0.0f : true<br>==0: false</td><td>String.valueOf()</td></tr><tr><td><strong>DOUBLE</strong></td><td>超出 INT32 范围：执行抛异常<br>否则：四舍五入(Math.round())</td><td>超出 INT64 范围：执行抛异常<br>否则：四舍五入(Math.round())</td><td>超出 FLOAT 范围：执行抛异常<br>否则：直接转化</td><td>不转化</td><td>!=0.0 : true<br>==0: false</td><td>String.valueOf()</td></tr><tr><td><strong>BOOLEAN</strong></td><td>true: 1<br>false: 0</td><td>true: 1L<br>false: 0</td><td>true: 1.0f<br>false: 0</td><td>true: 1.0<br>false: 0</td><td>不转化</td><td>true: "true"<br>false: "false"</td></tr><tr><td><strong>TEXT</strong></td><td>Integer.parseInt()</td><td>Long.parseLong()</td><td>Float.parseFloat()</td><td>Double.parseDouble()</td><td>text.toLowerCase =="true" : true<br>text.toLowerCase =="false" : false<br>其它情况：执行抛异常</td><td>不转化</td></tr></tbody></table><h4 id="使用示例" tabindex="-1"><a class="header-anchor" href="#使用示例" aria-hidden="true">#</a> 使用示例</h4><div class="language-text line-numbers-mode" data-ext="text"><pre class="language-text"><code>// timeseries |
| IoTDB> show timeseries root.sg.d1.** |
| +-------------+-----+--------+--------+--------+-----------+----+----------+--------+------------------+ |
| | Timeseries|Alias|Database|DataType|Encoding|Compression|Tags|Attributes|Deadband|DeadbandParameters| |
| +-------------+-----+--------+--------+--------+-----------+----+----------+--------+------------------+ |
| |root.sg.d1.s3| null| root.sg| FLOAT| PLAIN| SNAPPY|null| null| null| null| |
| |root.sg.d1.s4| null| root.sg| DOUBLE| PLAIN| SNAPPY|null| null| null| null| |
| |root.sg.d1.s5| null| root.sg| BOOLEAN| PLAIN| SNAPPY|null| null| null| null| |
| |root.sg.d1.s6| null| root.sg| TEXT| PLAIN| SNAPPY|null| null| null| null| |
| |root.sg.d1.s1| null| root.sg| INT32| PLAIN| SNAPPY|null| null| null| null| |
| |root.sg.d1.s2| null| root.sg| INT64| PLAIN| SNAPPY|null| null| null| null| |
| +-------------+-----+--------+--------+--------+-----------+----+----------+--------+------------------+ |
| |
| // data of timeseries |
| IoTDB> select * from root.sg.d1; |
| +-----------------------------+-------------+-------------+-------------+-------------+-------------+-------------+ |
| | Time|root.sg.d1.s3|root.sg.d1.s4|root.sg.d1.s5|root.sg.d1.s6|root.sg.d1.s1|root.sg.d1.s2| |
| +-----------------------------+-------------+-------------+-------------+-------------+-------------+-------------+ |
| |1970-01-01T08:00:00.000+08:00| 0.0| 0.0| false| 10000| 0| 0| |
| |1970-01-01T08:00:00.001+08:00| 1.0| 1.0| false| 3| 1| 1| |
| |1970-01-01T08:00:00.002+08:00| 2.7| 2.7| true| TRue| 2| 2| |
| |1970-01-01T08:00:00.003+08:00| 3.33| 3.33| true| faLse| 3| 3| |
| +-----------------------------+-------------+-------------+-------------+-------------+-------------+-------------+ |
| |
| // cast BOOLEAN to other types |
| IoTDB> select cast(s5 as INT32), cast(s5 as INT64),cast(s5 as FLOAT),cast(s5 as DOUBLE), cast(s5 as TEXT) from root.sg.d1 |
| +-----------------------------+----------------------------+----------------------------+----------------------------+-----------------------------+---------------------------+ |
| | Time|CAST(root.sg.d1.s5 AS INT32)|CAST(root.sg.d1.s5 AS INT64)|CAST(root.sg.d1.s5 AS FLOAT)|CAST(root.sg.d1.s5 AS DOUBLE)|CAST(root.sg.d1.s5 AS TEXT)| |
| +-----------------------------+----------------------------+----------------------------+----------------------------+-----------------------------+---------------------------+ |
| |1970-01-01T08:00:00.000+08:00| 0| 0| 0.0| 0.0| false| |
| |1970-01-01T08:00:00.001+08:00| 0| 0| 0.0| 0.0| false| |
| |1970-01-01T08:00:00.002+08:00| 1| 1| 1.0| 1.0| true| |
| |1970-01-01T08:00:00.003+08:00| 1| 1| 1.0| 1.0| true| |
| +-----------------------------+----------------------------+----------------------------+----------------------------+-----------------------------+---------------------------+ |
| |
| // cast TEXT to numeric types |
| IoTDB> select cast(s6 as INT32), cast(s6 as INT64), cast(s6 as FLOAT), cast(s6 as DOUBLE) from root.sg.d1 where time < 2 |
| +-----------------------------+----------------------------+----------------------------+----------------------------+-----------------------------+ |
| | Time|CAST(root.sg.d1.s6 AS INT32)|CAST(root.sg.d1.s6 AS INT64)|CAST(root.sg.d1.s6 AS FLOAT)|CAST(root.sg.d1.s6 AS DOUBLE)| |
| +-----------------------------+----------------------------+----------------------------+----------------------------+-----------------------------+ |
| |1970-01-01T08:00:00.000+08:00| 10000| 10000| 10000.0| 10000.0| |
| |1970-01-01T08:00:00.001+08:00| 3| 3| 3.0| 3.0| |
| +-----------------------------+----------------------------+----------------------------+----------------------------+-----------------------------+ |
| |
| // cast TEXT to BOOLEAN |
| IoTDB> select cast(s6 as BOOLEAN) from root.sg.d1 where time >= 2 |
| +-----------------------------+------------------------------+ |
| | Time|CAST(root.sg.d1.s6 AS BOOLEAN)| |
| +-----------------------------+------------------------------+ |
| |1970-01-01T08:00:00.002+08:00| true| |
| |1970-01-01T08:00:00.003+08:00| false| |
| +-----------------------------+------------------------------+ |
| </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 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>`,10);function a(l,o){return s(),t("div",null,[n(` |
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