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import{_ as t,r as o,o as p,c as l,b as s,d as n,a as i,e as a}from"./app-Bx8hKGcu.js";const c={},r=a(`<h1 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></h1><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><h2 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></h2><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-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><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><h3 id="使用场景" tabindex="-1"><a class="header-anchor" href="#使用场景"><span>使用场景</span></a></h3><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><span class="token comment"># insert 示例</span>
<span class="token keyword">insert</span> <span class="token keyword">into</span> root<span class="token punctuation">.</span>ln<span class="token punctuation">.</span>wf02<span class="token punctuation">.</span>wt02<span class="token punctuation">(</span><span class="token keyword">timestamp</span><span class="token punctuation">,</span>hardware<span class="token punctuation">)</span> <span class="token keyword">values</span><span class="token punctuation">(</span><span class="token number">1</span><span class="token punctuation">,</span> <span class="token string">&#39;v1&#39;</span><span class="token punctuation">)</span>
<span class="token keyword">insert</span> <span class="token keyword">into</span> root<span class="token punctuation">.</span>ln<span class="token punctuation">.</span>wf02<span class="token punctuation">.</span>wt02<span class="token punctuation">(</span><span class="token keyword">timestamp</span><span class="token punctuation">,</span>hardware<span class="token punctuation">)</span> <span class="token keyword">values</span><span class="token punctuation">(</span><span class="token number">2</span><span class="token punctuation">,</span> <span class="token string">&#39;\\\\&#39;</span><span class="token punctuation">)</span>
<span class="token operator">+</span><span class="token comment">-----------------------------+--------------------------+</span>
<span class="token operator">|</span> <span class="token keyword">Time</span><span class="token operator">|</span>root<span class="token punctuation">.</span>ln<span class="token punctuation">.</span>wf02<span class="token punctuation">.</span>wt02<span class="token punctuation">.</span>hardware<span class="token operator">|</span>
<span class="token operator">+</span><span class="token comment">-----------------------------+--------------------------+</span>
<span class="token operator">|</span><span class="token number">1970</span><span class="token operator">-</span><span class="token number">01</span><span class="token operator">-</span><span class="token number">01</span>T08:<span class="token number">00</span>:<span class="token number">00.001</span><span class="token operator">+</span><span class="token number">08</span>:<span class="token number">00</span><span class="token operator">|</span> v1<span class="token operator">|</span>
<span class="token operator">+</span><span class="token comment">-----------------------------+--------------------------+</span>
<span class="token operator">|</span><span class="token number">1970</span><span class="token operator">-</span><span class="token number">01</span><span class="token operator">-</span><span class="token number">01</span>T08:<span class="token number">00</span>:<span class="token number">00.002</span><span class="token operator">+</span><span class="token number">08</span>:<span class="token number">00</span><span class="token operator">|</span> \\\\<span class="token operator">|</span>
<span class="token operator">+</span><span class="token comment">-----------------------------+--------------------------+</span>
<span class="token comment"># select 示例</span>
<span class="token keyword">select</span> code <span class="token keyword">from</span> root<span class="token punctuation">.</span>sg1<span class="token punctuation">.</span>d1 <span class="token keyword">where</span> code <span class="token operator">in</span> <span class="token punctuation">(</span><span class="token string">&#39;string1&#39;</span><span class="token punctuation">,</span> <span class="token string">&#39;string2&#39;</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</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><span class="token comment"># load 示例</span>
<span class="token keyword">LOAD</span> <span class="token string">&#39;examplePath&#39;</span>
<span class="token comment"># remove 示例</span>
REMOVE <span class="token string">&#39;examplePath&#39;</span>
<span class="token comment"># SETTLE 示例</span>
SETTLE <span class="token string">&#39;examplePath&#39;</span>
</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><span class="token comment"># 示例，write_pwd 即为用户密码</span>
<span class="token keyword">CREATE</span> <span class="token keyword">USER</span> ln_write_user <span class="token string">&#39;write_pwd&#39;</span>
</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><span class="token comment"># 触发器示例，AS 后使用字符串表示类全类名</span>
<span class="token keyword">CREATE</span> <span class="token keyword">TRIGGER</span> <span class="token identifier"><span class="token punctuation">\`</span>alert-listener-sg1d1s1<span class="token punctuation">\`</span></span>
<span class="token keyword">AFTER</span> <span class="token keyword">INSERT</span>
<span class="token keyword">ON</span> root<span class="token punctuation">.</span>sg1<span class="token punctuation">.</span>d1<span class="token punctuation">.</span>s1
<span class="token keyword">AS</span> <span class="token string">&#39;org.apache.iotdb.db.engine.trigger.example.AlertListener&#39;</span>
<span class="token keyword">WITH</span> <span class="token punctuation">(</span>
<span class="token string">&#39;lo&#39;</span> <span class="token operator">=</span> <span class="token string">&#39;0&#39;</span><span class="token punctuation">,</span>
<span class="token string">&#39;hi&#39;</span> <span class="token operator">=</span> <span class="token string">&#39;100.0&#39;</span>
<span class="token punctuation">)</span>
<span class="token comment"># UDF 示例，AS 后使用字符串表示类全类名</span>
<span class="token keyword">CREATE</span> <span class="token keyword">FUNCTION</span> example <span class="token keyword">AS</span> <span class="token string">&#39;org.apache.iotdb.udf.UDTFExample&#39;</span>
</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><span class="token keyword">select</span> s1 <span class="token keyword">as</span> <span class="token string">&#39;temperature&#39;</span><span class="token punctuation">,</span> s2 <span class="token keyword">as</span> <span class="token string">&#39;speed&#39;</span> <span class="token keyword">from</span> root<span class="token punctuation">.</span>ln<span class="token punctuation">.</span>wf01<span class="token punctuation">.</span>wt01<span class="token punctuation">;</span>
<span class="token comment"># 表头如下所示</span>
<span class="token operator">+</span><span class="token comment">-----------------------------+-----------|-----+</span>
<span class="token operator">|</span> <span class="token keyword">Time</span><span class="token operator">|</span>temperature<span class="token operator">|</span>speed<span class="token operator">|</span>
<span class="token operator">+</span><span class="token comment">-----------------------------+-----------|-----+</span>
</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><h3 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></h3><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-text line-numbers-mode" data-ext="text" data-title="text"><pre class="language-text"><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><h2 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></h2><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><h2 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></h2>`,18),d={href:"https://iotdb.apache.org/zh/UserGuide/Master/Data-Concept/Data-Type.html",target:"_blank",rel:"noopener noreferrer"},u=a('<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><h2 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></h2><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><h2 id="空值" tabindex="-1"><a class="header-anchor" href="#空值"><span>空值</span></a></h2><p><code>NULL</code>值表示没有数据。<code>NULL</code>对大小写不敏感。</p>',5);function k(m,v){const e=o("ExternalLinkIcon");return p(),l("div",null,[r,s("p",null,[n("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 "),s("a",d,[n("数据类型文档"),i(e)]),n("。")]),u])}const g=t(c,[["render",k],["__file","Literal-Values.html.vue"]]),h=JSON.parse(`{"path":"/zh/UserGuide/V1.0.x/Syntax-Conventions/Literal-Values.html","title":"字面值常量","lang":"zh-CN","frontmatter":{"description":"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 / SETTLE ...","head":[["link",{"rel":"alternate","hreflang":"en-us","href":"https://iotdb.apache.org/UserGuide/V1.0.x/Syntax-Conventions/Literal-Values.html"}],["meta",{"property":"og:url","content":"https://iotdb.apache.org/zh/UserGuide/V1.0.x/Syntax-Conventions/Literal-Values.html"}],["meta",{"property":"og:site_name","content":"IoTDB Website"}],["meta",{"property":"og:title","content":"字面值常量"}],["meta",{"property":"og:description","content":"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 / SETTLE ..."}],["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\\":\\"字面值常量\\",\\"image\\":[\\"\\"],\\"dateModified\\":\\"2023-07-10T03:11:17.000Z\\",\\"author\\":[]}"]]},"headers":[{"level":2,"title":"字符串常量","slug":"字符串常量","link":"#字符串常量","children":[{"level":3,"title":"使用场景","slug":"使用场景","link":"#使用场景","children":[]},{"level":3,"title":"如何在字符串内使用引号","slug":"如何在字符串内使用引号","link":"#如何在字符串内使用引号","children":[]}]},{"level":2,"title":"数值型常量","slug":"数值型常量","link":"#数值型常量","children":[]},{"level":2,"title":"时间戳常量","slug":"时间戳常量","link":"#时间戳常量","children":[]},{"level":2,"title":"布尔型常量","slug":"布尔型常量","link":"#布尔型常量","children":[]},{"level":2,"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":3.02,"words":907},"filePathRelative":"zh/UserGuide/V1.0.x/Syntax-Conventions/Literal-Values.md","localizedDate":"2023年7月10日","autoDesc":true}`);export{g as comp,h as data};