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apache / iotdb-website / 7d17d2d476e55c0f45d021da19e24450fc56ebbd / . / assets / Literal-Values.html-DWHyclxT.js
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import{_ as d,r as l,o as t,c as s,b as i,d as e,a as r,e as n}from"./app-Bp5kEZWW.js";const o={},c=n(`<h1 id="语法约定" tabindex="-1"><a class="header-anchor" href="#语法约定"><span>语法约定</span></a></h1><h2 id="字面值常量" tabindex="-1"><a class="header-anchor" href="#字面值常量"><span>字面值常量</span></a></h2><p>该部分对 IoTDB 中支持的字面值常量进行说明，包括字符串常量、数值型常量、时间戳常量、布尔型常量和空值。</p><h3 id="字符串常量" tabindex="-1"><a class="header-anchor" href="#字符串常量"><span>字符串常量</span></a></h3><p>在 IoTDB 中，字符串是由<strong>单引号（<code>&#39;</code>）或双引号（<code>&quot;</code>）字符括起来的字符序列</strong>。示例如下：</p><div class="language-Plain%20Text line-numbers-mode" data-ext="Plain%20Text" data-title="Plain%20Text"><pre class="language-Plain%20Text"><code>&#39;a string&#39;
&quot;another string&quot;
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div></div></div><h4 id="使用场景" tabindex="-1"><a class="header-anchor" href="#使用场景"><span>使用场景</span></a></h4><ul><li><p><code>INSERT</code> 或者 <code>SELECT</code> 中用于表达 <code>TEXT</code> 类型数据的场景。</p><div class="language-SQL line-numbers-mode" data-ext="SQL" data-title="SQL"><pre class="language-SQL"><code># insert 示例
insert into root.ln.wf02.wt02(timestamp,hardware) values(1, &#39;v1&#39;)
insert into root.ln.wf02.wt02(timestamp,hardware) values(2, &#39;\\\\&#39;)
+-----------------------------+--------------------------+
| Time|root.ln.wf02.wt02.hardware|
+-----------------------------+--------------------------+
|1970-01-01T08:00:00.001+08:00| v1|
+-----------------------------+--------------------------+
|1970-01-01T08:00:00.002+08:00| \\\\|
+-----------------------------+--------------------------+
# select 示例
select code from root.sg1.d1 where code in (&#39;string1&#39;, &#39;string2&#39;);
</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></li><li><p><code>LOAD</code> / <code>REMOVE</code> / <code>SETTLE</code> 指令中的文件路径。</p><div class="language-SQL line-numbers-mode" data-ext="SQL" data-title="SQL"><pre class="language-SQL"><code># load 示例
LOAD &#39;examplePath&#39;
# remove 示例
REMOVE &#39;examplePath&#39;
# SETTLE 示例
SETTLE &#39;examplePath&#39;
</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></div></li><li><p>用户密码。</p><div class="language-SQL line-numbers-mode" data-ext="SQL" data-title="SQL"><pre class="language-SQL"><code># 示例，write_pwd 即为用户密码
CREATE USER ln_write_user &#39;write_pwd&#39;
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div></div></div></li><li><p>触发器和 UDF 中的类全类名，示例如下：</p><div class="language-SQL line-numbers-mode" data-ext="SQL" data-title="SQL"><pre class="language-SQL"><code># 触发器示例，AS 后使用字符串表示类全类名
CREATE TRIGGER \`alert-listener-sg1d1s1\`
AFTER INSERT
ON root.sg1.d1.s1
AS &#39;org.apache.iotdb.db.engine.trigger.example.AlertListener&#39;
WITH (
&#39;lo&#39; = &#39;0&#39;,
&#39;hi&#39; = &#39;100.0&#39;
)
# UDF 示例，AS 后使用字符串表示类全类名
CREATE FUNCTION example AS &#39;org.apache.iotdb.udf.UDTFExample&#39;
</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></li><li><p>Select 子句中可以为结果集中的值指定别名，别名可以被定义为字符串或者标识符，示例如下：</p><div class="language-SQL line-numbers-mode" data-ext="SQL" data-title="SQL"><pre class="language-SQL"><code>select s1 as &#39;temperature&#39;, s2 as &#39;speed&#39; from root.ln.wf01.wt01;
# 表头如下所示
+-----------------------------+-----------|-----+
| Time|temperature|speed|
+-----------------------------+-----------|-----+
</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></li><li><p>用于表示键值对，键值对的键和值可以被定义成常量（包括字符串）或者标识符，具体请参考键值对章节。</p></li></ul><h4 id="如何在字符串内使用引号" tabindex="-1"><a class="header-anchor" href="#如何在字符串内使用引号"><span>如何在字符串内使用引号</span></a></h4><ul><li>在单引号引起的字符串内，双引号无需特殊处理。同理，在双引号引起的字符串内，单引号无需特殊处理。</li><li>在单引号引起的字符串里，可以通过双写单引号来表示一个单引号，即单引号 &#39; 可以表示为 &#39;&#39;。</li><li>在双引号引起的字符串里，可以通过双写双引号来表示一个双引号，即双引号 &quot; 可以表示为 &quot;&quot;。</li></ul><p>字符串内使用引号的示例如下：</p><div class="language-Plain%20Text line-numbers-mode" data-ext="Plain%20Text" data-title="Plain%20Text"><pre class="language-Plain%20Text"><code>&#39;string&#39; // string
&#39;&quot;string&quot;&#39; // &quot;string&quot;
&#39;&quot;&quot;string&quot;&quot;&#39; // &quot;&quot;string&quot;&quot;
&#39;&#39;&#39;string&#39; // &#39;string
&quot;string&quot; // string
&quot;&#39;string&#39;&quot; // &#39;string&#39;
&quot;&#39;&#39;string&#39;&#39;&quot; // &#39;&#39;string&#39;&#39;
&quot;&quot;&quot;string&quot; // &quot;string
</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><h3 id="数值型常量" tabindex="-1"><a class="header-anchor" href="#数值型常量"><span>数值型常量</span></a></h3><p>数值型常量包括整型和浮点型。</p><p>整型常量是一个数字序列。可以以 <code>+</code> 或 <code>-</code> 开头表示正负。例如：<code>1</code>, <code>-1</code>。</p><p>带有小数部分或由科学计数法表示的为浮点型常量，例如：<code>.1</code>, <code>3.14</code>, <code>-2.23</code>, <code>+1.70</code>, <code>1.2E3</code>, <code>1.2E-3</code>, <code>-1.2E3</code>, <code>-1.2E-3</code>。</p><p>在 IoTDB 中，<code>INT32</code> 和 <code>INT64</code> 表示整数类型（计算是准确的），<code>FLOAT</code> 和 <code>DOUBLE</code> 表示浮点数类型（计算是近似的）。</p><p>在浮点上下文中可以使用整数，它会被解释为等效的浮点数。</p><h3 id="时间戳常量" tabindex="-1"><a class="header-anchor" href="#时间戳常量"><span>时间戳常量</span></a></h3>`,19),u={href:"https://iotdb.apache.org/zh/UserGuide/Master/Data-Concept/Data-Type.html",target:"_blank",rel:"noopener noreferrer"},v=n('<p>特别地，<code>NOW()</code>表示语句开始执行时的服务端系统时间戳。</p><h3 id="布尔型常量" tabindex="-1"><a class="header-anchor" href="#布尔型常量"><span>布尔型常量</span></a></h3><p>布尔值常量 <code>TRUE</code> 和 <code>FALSE</code> 分别等价于 <code>1</code> 和 <code>0</code>，它们对大小写不敏感。</p><h3 id="空值" tabindex="-1"><a class="header-anchor" href="#空值"><span>空值</span></a></h3><p><code>NULL</code>值表示没有数据。<code>NULL</code>对大小写不敏感。</p>',5);function m(p,h){const a=l("ExternalLinkIcon");return t(),s("div",null,[c,i("p",null,[e("时间戳是一个数据到来的时间点，在 IoTDB 中分为绝对时间戳和相对时间戳。详细信息可参考 "),i("a",u,[e("数据类型文档"),r(a)]),e("。")]),v])}const g=d(o,[["render",m],["__file","Literal-Values.html.vue"]]),T=JSON.parse(`{"path":"/zh/UserGuide/V1.1.x/Syntax-Conventions/Literal-Values.html","title":"语法约定","lang":"zh-CN","frontmatter":{"description":"语法约定 字面值常量 该部分对 IoTDB 中支持的字面值常量进行说明，包括字符串常量、数值型常量、时间戳常量、布尔型常量和空值。 字符串常量 在 IoTDB 中，字符串是由单引号（'）或双引号（\\"）字符括起来的字符序列。示例如下： 使用场景 INSERT 或者 SELECT 中用于表达 TEXT 类型数据的场景。 LOAD / REMOVE / SE...","head":[["link",{"rel":"alternate","hreflang":"en-us","href":"https://iotdb.apache.org/UserGuide/V1.1.x/Syntax-Conventions/Literal-Values.html"}],["meta",{"property":"og:url","content":"https://iotdb.apache.org/zh/UserGuide/V1.1.x/Syntax-Conventions/Literal-Values.html"}],["meta",{"property":"og:site_name","content":"IoTDB Website"}],["meta",{"property":"og:title","content":"语法约定"}],["meta",{"property":"og:description","content":"语法约定 字面值常量 该部分对 IoTDB 中支持的字面值常量进行说明，包括字符串常量、数值型常量、时间戳常量、布尔型常量和空值。 字符串常量 在 IoTDB 中，字符串是由单引号（'）或双引号（\\"）字符括起来的字符序列。示例如下： 使用场景 INSERT 或者 SELECT 中用于表达 TEXT 类型数据的场景。 LOAD / REMOVE / SE..."}],["meta",{"property":"og:type","content":"article"}],["meta",{"property":"og:locale","content":"zh-CN"}],["meta",{"property":"og:locale:alternate","content":"en-US"}],["meta",{"property":"og:updated_time","content":"2023-07-10T03:11:17.000Z"}],["meta",{"property":"article:modified_time","content":"2023-07-10T03:11:17.000Z"}],["script",{"type":"application/ld+json"},"{\\"@context\\":\\"https://schema.org\\",\\"@type\\":\\"Article\\",\\"headline\\":\\"语法约定\\",\\"image\\":[\\"\\"],\\"dateModified\\":\\"2023-07-10T03:11:17.000Z\\",\\"author\\":[]}"]]},"headers":[{"level":2,"title":"字面值常量","slug":"字面值常量","link":"#字面值常量","children":[{"level":3,"title":"字符串常量","slug":"字符串常量","link":"#字符串常量","children":[]},{"level":3,"title":"数值型常量","slug":"数值型常量","link":"#数值型常量","children":[]},{"level":3,"title":"时间戳常量","slug":"时间戳常量","link":"#时间戳常量","children":[]},{"level":3,"title":"布尔型常量","slug":"布尔型常量","link":"#布尔型常量","children":[]},{"level":3,"title":"空值","slug":"空值","link":"#空值","children":[]}]}],"git":{"createdTime":1688958677000,"updatedTime":1688958677000,"contributors":[{"name":"CritasWang","email":"critas@outlook.com","commits":1}]},"readingTime":{"minutes":3.05,"words":915},"filePathRelative":"zh/UserGuide/V1.1.x/Syntax-Conventions/Literal-Values.md","localizedDate":"2023年7月10日","autoDesc":true}`);export{g as comp,T as data};