| import{_ as s,O as e,P as n,ah as t,aW as a}from"./framework-e4340ccd.js";const i={},o=a(`<h1 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</h1><h2 id="cast" tabindex="-1"><a class="header-anchor" href="#cast" aria-hidden="true">#</a> CAST</h2><h3 id="函数简介" tabindex="-1"><a class="header-anchor" href="#函数简介" aria-hidden="true">#</a> 函数简介</h3><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。所以,IoTDB支持使用cast函数对数据类型进行转换。</p><table><thead><tr><th>函数名</th><th>必要的属性参数</th><th>输出序列类型</th><th>功能类型</th></tr></thead><tbody><tr><td>CAST</td><td><code>type</code>:输出的数据点的类型,只能是 INT32 / INT64 / FLOAT / DOUBLE / BOOLEAN / TEXT</td><td>由输入属性参数<code>type</code>决定</td><td>将数据转换为<code>type</code>参数指定的类型。</td></tr></tbody></table><h3 id="类型转换说明" tabindex="-1"><a class="header-anchor" href="#类型转换说明" aria-hidden="true">#</a> 类型转换说明</h3><p>1.当INT32、INT64类型的值不为0时,FLOAT与DOUBLE类型的值不为0.0时,TEXT类型不为空字符串或者"false"时,转换为BOOLEAN类型时值为true,否则为false。</p><div class="language-text line-numbers-mode" data-ext="text"><pre class="language-text"><code>IoTDB> show timeseries root.sg.d1.*; |
| +-------------+-----+-------------+--------+--------+-----------+----+----------+ |
| | timeseries|alias| database|dataType|encoding|compression|tags|attributes| |
| +-------------+-----+-------------+--------+--------+-----------+----+----------+ |
| |root.sg.d1.s3| null| root.sg| FLOAT| RLE| SNAPPY|null| null| |
| |root.sg.d1.s4| null| root.sg| DOUBLE| RLE| SNAPPY|null| null| |
| |root.sg.d1.s5| null| root.sg| TEXT| PLAIN| SNAPPY|null| null| |
| |root.sg.d1.s6| null| root.sg| BOOLEAN| RLE| SNAPPY|null| null| |
| |root.sg.d1.s1| null| root.sg| INT32| RLE| SNAPPY|null| null| |
| |root.sg.d1.s2| null| root.sg| INT64| RLE| SNAPPY|null| null| |
| +-------------+-----+-------------+--------+--------+-----------+----+----------+ |
| Total line number = 6 |
| It costs 0.006s |
| 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| |
| +-----------------------------+-------------+-------------+-------------+-------------+-------------+-------------+ |
| |1970-01-01T08:00:00.001+08:00| 1.1| 1.1| test| false| 1| 1| |
| |1970-01-01T08:00:00.002+08:00| -2.2| -2.2| false| true| -2| -2| |
| |1970-01-01T08:00:00.003+08:00| 0.0| 0.0| true| true| 0| 0| |
| +-----------------------------+-------------+-------------+-------------+-------------+-------------+-------------+ |
| Total line number = 3 |
| It costs 0.009s |
| IoTDB> select cast(s1, 'type'='BOOLEAN'), cast(s2, 'type'='BOOLEAN'), cast(s3, 'type'='BOOLEAN'), cast(s4, 'type'='BOOLEAN'), cast(s5, 'type'='BOOLEAN') from root.sg.d1; |
| +-----------------------------+-------------------------------------+-------------------------------------+-------------------------------------+-------------------------------------+-------------------------------------+ |
| | Time|cast(root.sg.d1.s1, "type"="BOOLEAN")|cast(root.sg.d1.s2, "type"="BOOLEAN")|cast(root.sg.d1.s3, "type"="BOOLEAN")|cast(root.sg.d1.s4, "type"="BOOLEAN")|cast(root.sg.d1.s5, "type"="BOOLEAN")| |
| +-----------------------------+-------------------------------------+-------------------------------------+-------------------------------------+-------------------------------------+-------------------------------------+ |
| |1970-01-01T08:00:00.001+08:00| true| true| true| true| true| |
| |1970-01-01T08:00:00.002+08:00| true| true| true| true| false| |
| |1970-01-01T08:00:00.003+08:00| false| false| false| false| true| |
| +-----------------------------+-------------------------------------+-------------------------------------+-------------------------------------+-------------------------------------+-------------------------------------+ |
| Total line number = 3 |
| 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 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>2.当BOOLEAN类型的值为true时,转换为INT32与INT64类型的值为1,转换为FLOAT或者DOUBLE类型时值为1.0,转换为TEXT类型时值为"true"。当BOOLEAN类型的值为false时,转换为INT32与INT64类型的值为0,转换为FLOAT或者DOUBLE类型时值为0.0,转换为TEXT类型时值为"false"。</p><div class="language-text line-numbers-mode" data-ext="text"><pre class="language-text"><code>IoTDB> select cast(s6, 'type'='INT32'), cast(s6, 'type'='INT64'), cast(s6, 'type'='FLOAT'), cast(s6, 'type'='DOUBLE'), cast(s6, 'type'='TEXT') from root.sg.d1; |
| +-----------------------------+-----------------------------------+-----------------------------------+-----------------------------------+------------------------------------+----------------------------------+ |
| | Time|cast(root.sg.d1.s6, "type"="INT32")|cast(root.sg.d1.s6, "type"="INT64")|cast(root.sg.d1.s6, "type"="FLOAT")|cast(root.sg.d1.s6, "type"="DOUBLE")|cast(root.sg.d1.s6, "type"="TEXT")| |
| +-----------------------------+-----------------------------------+-----------------------------------+-----------------------------------+------------------------------------+----------------------------------+ |
| |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| |
| +-----------------------------+-----------------------------------+-----------------------------------+-----------------------------------+------------------------------------+----------------------------------+ |
| Total line number = 3 |
| 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 class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>3.当TEXT类型转换为INT32、INT64、FLOAT类型时,会先将TEXT类型的数据转换为DOUBLE类型,然后再转换为对应的类型,此时可能会存在损失精度的问题。如果无法转换的话则直接跳过。</p><div class="language-text line-numbers-mode" data-ext="text"><pre class="language-text"><code>IoTDB> select cast(s5, 'type'='INT32'), cast(s5, 'type'='INT64'), cast(s5, 'type'='FLOAT') from root.sg.d1; |
| +----+-----------------------------------+-----------------------------------+-----------------------------------+ |
| |Time|cast(root.sg.d1.s5, "type"="INT32")|cast(root.sg.d1.s5, "type"="INT64")|cast(root.sg.d1.s5, "type"="FLOAT")| |
| +----+-----------------------------------+-----------------------------------+-----------------------------------+ |
| +----+-----------------------------------+-----------------------------------+-----------------------------------+ |
| Empty set. |
| 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><h3 id="使用示例" tabindex="-1"><a class="header-anchor" href="#使用示例" aria-hidden="true">#</a> 使用示例</h3><p>测试数据:</p><div class="language-text line-numbers-mode" data-ext="text"><pre class="language-text"><code>IoTDB> select text from root.test; |
| +-----------------------------+--------------+ |
| | Time|root.test.text| |
| +-----------------------------+--------------+ |
| |1970-01-01T08:00:00.001+08:00| 1.1| |
| |1970-01-01T08:00:00.002+08:00| 1| |
| |1970-01-01T08:00:00.003+08:00| hello world| |
| |1970-01-01T08:00:00.004+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></div><p>SQL语句:</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><span class="token keyword">text</span><span class="token punctuation">,</span> <span class="token string">'type'</span><span class="token operator">=</span><span class="token string">'BOOLEAN'</span><span class="token punctuation">)</span><span class="token punctuation">,</span> cast<span class="token punctuation">(</span><span class="token keyword">text</span><span class="token punctuation">,</span> <span class="token string">'type'</span><span class="token operator">=</span><span class="token string">'INT32'</span><span class="token punctuation">)</span><span class="token punctuation">,</span> cast<span class="token punctuation">(</span><span class="token keyword">text</span><span class="token punctuation">,</span> <span class="token string">'type'</span><span class="token operator">=</span><span class="token string">'INT64'</span><span class="token punctuation">)</span><span class="token punctuation">,</span> cast<span class="token punctuation">(</span><span class="token keyword">text</span><span class="token punctuation">,</span> <span class="token string">'type'</span><span class="token operator">=</span><span class="token string">'FLOAT'</span><span class="token punctuation">)</span><span class="token punctuation">,</span> cast<span class="token punctuation">(</span><span class="token keyword">text</span><span class="token punctuation">,</span> <span class="token string">'type'</span><span class="token operator">=</span><span class="token string">'DOUBLE'</span><span class="token punctuation">)</span> <span class="token keyword">from</span> root<span class="token punctuation">.</span>test<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|cast(root.test.text, "type"="BOOLEAN")|cast(root.test.text, "type"="INT32")|cast(root.test.text, "type"="INT64")|cast(root.test.text, "type"="FLOAT")|cast(root.test.text, "type"="DOUBLE")| |
| +-----------------------------+--------------------------------------+------------------------------------+------------------------------------+------------------------------------+-------------------------------------+ |
| |1970-01-01T08:00:00.001+08:00| true| 1| 1| 1.1| 1.1| |
| |1970-01-01T08:00:00.002+08:00| true| 1| 1| 1.0| 1.0| |
| |1970-01-01T08:00:00.003+08:00| true| null| null| null| null| |
| |1970-01-01T08:00:00.004+08:00| false| null| null| null| null| |
| +-----------------------------+--------------------------------------+------------------------------------+------------------------------------+------------------------------------+-------------------------------------+ |
| Total line number = 4 |
| It costs 0.078s |
| </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></div>`,19);function l(d,u){return e(),n("div",null,[t(` |
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| or more contributor license agreements. See the NOTICE file |
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| regarding copyright ownership. The ASF licenses this file |
| to you under the Apache License, Version 2.0 (the |
| "License"); you may not use this file except in compliance |
| with the License. You may obtain a copy of the License at |
| |
| http://www.apache.org/licenses/LICENSE-2.0 |
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| software distributed under the License is distributed on an |
| "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY |
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| specific language governing permissions and limitations |
| under the License. |
| |
| `),o])}const c=s(i,[["render",l],["__file","Conversion.html.vue"]]);export{c as default}; |