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class="router-link-active router-link-exact-active nav-link sidebar-link heading" aria-label="数值型常量"><!---->数值型常量<!----></a><ul class="sidebar-sub-headers"></ul></li><li class="sidebar-sub-header"><a aria-current="page" href="/zh/UserGuide/V0.13.x/Reference/Syntax-Conventions.html#时间戳常量" class="router-link-active router-link-exact-active nav-link sidebar-link heading" aria-label="时间戳常量"><!---->时间戳常量<!----></a><ul class="sidebar-sub-headers"></ul></li><li class="sidebar-sub-header"><a aria-current="page" href="/zh/UserGuide/V0.13.x/Reference/Syntax-Conventions.html#布尔型常量" class="router-link-active router-link-exact-active nav-link sidebar-link heading" aria-label="布尔型常量"><!---->布尔型常量<!----></a><ul class="sidebar-sub-headers"></ul></li><li class="sidebar-sub-header"><a aria-current="page" href="/zh/UserGuide/V0.13.x/Reference/Syntax-Conventions.html#空值" class="router-link-active router-link-exact-active nav-link sidebar-link heading" aria-label="空值"><!---->空值<!----></a><ul class="sidebar-sub-headers"></ul></li></ul></li><li class="sidebar-sub-header"><a aria-current="page" href="/zh/UserGuide/V0.13.x/Reference/Syntax-Conventions.html#标识符" class="router-link-active router-link-exact-active nav-link sidebar-link heading" aria-label="标识符"><!---->标识符<!----></a><ul class="sidebar-sub-headers"></ul></li><li class="sidebar-sub-header"><a aria-current="page" href="/zh/UserGuide/V0.13.x/Reference/Syntax-Conventions.html#路径节点名" class="router-link-active router-link-exact-active nav-link sidebar-link heading" aria-label="路径节点名"><!---->路径节点名<!----></a><ul class="sidebar-sub-headers"></ul></li><li class="sidebar-sub-header"><a aria-current="page" href="/zh/UserGuide/V0.13.x/Reference/Syntax-Conventions.html#关键字和保留字" class="router-link-active router-link-exact-active nav-link sidebar-link heading" aria-label="关键字和保留字"><!---->关键字和保留字<!----></a><ul class="sidebar-sub-headers"></ul></li><li class="sidebar-sub-header"><a aria-current="page" href="/zh/UserGuide/V0.13.x/Reference/Syntax-Conventions.html#表达式" class="router-link-active router-link-exact-active nav-link sidebar-link heading" aria-label="表达式"><!---->表达式<!----></a><ul class="sidebar-sub-headers"></ul></li><li class="sidebar-sub-header"><a aria-current="page" href="/zh/UserGuide/V0.13.x/Reference/Syntax-Conventions.html#引用符号" class="router-link-active router-link-exact-active nav-link sidebar-link heading" aria-label="引用符号"><!---->引用符号<!----></a><ul class="sidebar-sub-headers"><li class="sidebar-sub-header"><a aria-current="page" href="/zh/UserGuide/V0.13.x/Reference/Syntax-Conventions.html#双引号-、单引号" class="router-link-active router-link-exact-active nav-link sidebar-link heading" aria-label="双引号（"）、单引号（'）"><!---->双引号（"）、单引号（'）<!----></a><ul class="sidebar-sub-headers"></ul></li><li class="sidebar-sub-header"><a aria-current="page" href="/zh/UserGuide/V0.13.x/Reference/Syntax-Conventions.html#反引号" class="router-link-active router-link-exact-active nav-link sidebar-link heading" aria-label="反引号（`）"><!---->反引号（`）<!----></a><ul class="sidebar-sub-headers"></ul></li><li class="sidebar-sub-header"><a aria-current="page" href="/zh/UserGuide/V0.13.x/Reference/Syntax-Conventions.html#反斜杠" class="router-link-active router-link-exact-active nav-link sidebar-link heading" aria-label="反斜杠（\）"><!---->反斜杠（\）<!----></a><ul class="sidebar-sub-headers"></ul></li></ul></li><li class="sidebar-sub-header"><a aria-current="page" href="/zh/UserGuide/V0.13.x/Reference/Syntax-Conventions.html#了解更多" class="router-link-active router-link-exact-active nav-link sidebar-link heading" aria-label="了解更多"><!---->了解更多<!----></a><ul class="sidebar-sub-headers"></ul></li></ul><!--]--></li></ul></section></li><li><section class="sidebar-group"><button class="sidebar-heading clickable"><!----><span class="title">应用编程接口</span><span class="arrow end"></span></button><!----></section></li><li><section class="sidebar-group"><button class="sidebar-heading clickable"><!----><span class="title">元数据操作</span><span class="arrow end"></span></button><!----></section></li><li><section class="sidebar-group"><button class="sidebar-heading clickable"><!----><span class="title">数据写入和删除</span><span class="arrow end"></span></button><!----></section></li><li><section class="sidebar-group"><button class="sidebar-heading clickable"><!----><span class="title">数据查询</span><span class="arrow end"></span></button><!----></section></li><li><section class="sidebar-group"><button class="sidebar-heading clickable"><!----><span class="title">数据处理</span><span class="arrow end"></span></button><!----></section></li><li><section class="sidebar-group"><button class="sidebar-heading clickable"><!----><span class="title">权限管理</span><span class="arrow end"></span></button><!----></section></li><li><section class="sidebar-group"><button class="sidebar-heading clickable"><!----><span class="title">运维工具</span><span class="arrow end"></span></button><!----></section></li><li><section class="sidebar-group"><button class="sidebar-heading clickable"><!----><span class="title">系统集成</span><span class="arrow end"></span></button><!----></section></li><li><section class="sidebar-group"><button class="sidebar-heading clickable"><!----><span class="title">UDF 资料库</span><span class="arrow end"></span></button><!----></section></li><li><section class="sidebar-group"><button class="sidebar-heading clickable"><!----><span class="title">参考</span><span class="arrow end"></span></button><!----></section></li></ul><!--[--><!----><!--]--></aside><!--[--><main class="page" id="main-content"><!--[--><!----><nav class="breadcrumb disable"></nav><div class="page-title"><h1><!---->语法约定</h1><div class="page-info"><!----><!----><!----><!----><span class="page-reading-time-info" aria-label="阅读时间"><svg xmlns="http://www.w3.org/2000/svg" class="icon timer-icon" viewBox="0 0 1024 1024" fill="currentColor" aria-label="timer icon"><path d="M799.387 122.15c4.402-2.978 7.38-7.897 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class="router-link-active router-link-exact-active toc-link level2">字面值常量</a></li><ul class="toc-list"><!--[--><li class="toc-item"><a aria-current="page" href="/zh/UserGuide/V0.13.x/Reference/Syntax-Conventions.html#字符串常量" class="router-link-active router-link-exact-active toc-link level3">字符串常量</a></li><!----><!--]--><!--[--><li class="toc-item"><a aria-current="page" href="/zh/UserGuide/V0.13.x/Reference/Syntax-Conventions.html#数值型常量" class="router-link-active router-link-exact-active toc-link level3">数值型常量</a></li><!----><!--]--><!--[--><li class="toc-item"><a aria-current="page" href="/zh/UserGuide/V0.13.x/Reference/Syntax-Conventions.html#时间戳常量" class="router-link-active router-link-exact-active toc-link level3">时间戳常量</a></li><!----><!--]--><!--[--><li class="toc-item"><a aria-current="page" href="/zh/UserGuide/V0.13.x/Reference/Syntax-Conventions.html#布尔型常量" class="router-link-active router-link-exact-active toc-link level3">布尔型常量</a></li><!----><!--]--><!--[--><li class="toc-item"><a aria-current="page" href="/zh/UserGuide/V0.13.x/Reference/Syntax-Conventions.html#空值" class="router-link-active router-link-exact-active toc-link level3">空值</a></li><!----><!--]--></ul><!--]--><!--[--><li class="toc-item"><a aria-current="page" href="/zh/UserGuide/V0.13.x/Reference/Syntax-Conventions.html#标识符" class="router-link-active router-link-exact-active toc-link level2">标识符</a></li><!----><!--]--><!--[--><li class="toc-item"><a aria-current="page" href="/zh/UserGuide/V0.13.x/Reference/Syntax-Conventions.html#路径节点名" class="router-link-active router-link-exact-active toc-link level2">路径节点名</a></li><!----><!--]--><!--[--><li class="toc-item"><a aria-current="page" href="/zh/UserGuide/V0.13.x/Reference/Syntax-Conventions.html#关键字和保留字" class="router-link-active router-link-exact-active toc-link level2">关键字和保留字</a></li><!----><!--]--><!--[--><li class="toc-item"><a aria-current="page" href="/zh/UserGuide/V0.13.x/Reference/Syntax-Conventions.html#表达式" class="router-link-active router-link-exact-active toc-link level2">表达式</a></li><!----><!--]--><!--[--><li class="toc-item"><a aria-current="page" href="/zh/UserGuide/V0.13.x/Reference/Syntax-Conventions.html#引用符号" class="router-link-active router-link-exact-active toc-link level2">引用符号</a></li><ul class="toc-list"><!--[--><li class="toc-item"><a aria-current="page" href="/zh/UserGuide/V0.13.x/Reference/Syntax-Conventions.html#双引号-、单引号" class="router-link-active router-link-exact-active toc-link level3">双引号（"）、单引号（'）</a></li><!----><!--]--><!--[--><li class="toc-item"><a aria-current="page" href="/zh/UserGuide/V0.13.x/Reference/Syntax-Conventions.html#反引号" class="router-link-active router-link-exact-active toc-link level3">反引号（`）</a></li><!----><!--]--><!--[--><li class="toc-item"><a aria-current="page" href="/zh/UserGuide/V0.13.x/Reference/Syntax-Conventions.html#反斜杠" class="router-link-active router-link-exact-active toc-link level3">反斜杠（\）</a></li><!----><!--]--></ul><!--]--><!--[--><li class="toc-item"><a aria-current="page" href="/zh/UserGuide/V0.13.x/Reference/Syntax-Conventions.html#了解更多" class="router-link-active router-link-exact-active toc-link level2">了解更多</a></li><!----><!--]--></ul></div><!--[--><!----><!--]--></aside></div><!----><div class="theme-hope-content"><!-- |
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| --><h1 id="语法约定" tabindex="-1"><a class="header-anchor" href="#语法约定" aria-hidden="true">#</a> 语法约定</h1><h2 id="字面值常量" tabindex="-1"><a class="header-anchor" href="#字面值常量" aria-hidden="true">#</a> 字面值常量</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" aria-hidden="true">#</a> 字符串常量</h3><p>字符串是由单引号（<code>'</code>）或双引号（<code>"</code>）字符括起来的字符序列。示例如下：</p><div class="language-javascript line-numbers-mode" data-ext="js"><pre class="language-javascript"><code><span class="token string">'a string'</span> |
| <span class="token string">"another string"</span> |
| </code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div></div></div><p>字符串字面值的使用场景：</p><ul><li><code>INSERT</code> 或者 <code>SELECT</code> 中用于表达 <code>TEXT</code> 类型数据的场景</li><li>SQL 中 UDF 和 Trigger 的 Java 类全类名</li><li><code>CREATE TRIGGER</code> 语句中描述触发器属性的键值对</li><li>UDF 函数输入参数中的属性</li><li><code>LOAD</code> / <code>REMOVE</code> / <code>SETTLE</code> 指令中的文件路径</li><li>用户密码</li></ul><p>通过以下几种方式可以在字符串内使用引号：</p><ul><li>在引号前使用转义符 (\)。</li><li>在单引号括的的字符串内，双引号无需特殊处理。同理，在双引号括的的字符串内，单引号无需特殊处理。</li></ul><p>关于引号和转义字符的使用示例如下：</p><div class="language-javascript line-numbers-mode" data-ext="js"><pre class="language-javascript"><code><span class="token string">'string'</span> <span class="token comment">// string</span> |
| <span class="token string">'"string"'</span> <span class="token comment">// "string"</span> |
| <span class="token string">'""string""'</span> <span class="token comment">// ""string""</span> |
| <span class="token string">'str\'ing'</span> <span class="token comment">// str'ing</span> |
| <span class="token string">'\'string'</span> <span class="token comment">// 'string</span> |
| <span class="token string">"string"</span> <span class="token comment">// string</span> |
| <span class="token string">"'string'"</span> <span class="token comment">// 'string'</span> |
| <span class="token string">"''string''"</span> <span class="token comment">// ''string''</span> |
| <span class="token string">"str\"ing"</span> <span class="token comment">// str"ing</span> |
| <span class="token string">"\"string"</span> <span class="token comment">// "string</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></div><h3 id="数值型常量" tabindex="-1"><a class="header-anchor" href="#数值型常量" aria-hidden="true">#</a> 数值型常量</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" aria-hidden="true">#</a> 时间戳常量</h3><p>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 <a href="/zh/UserGuide/V0.13.x/Data-Concept/Data-Type.html" class="">数据类型文档</a>。</p><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" aria-hidden="true">#</a> 布尔型常量</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" aria-hidden="true">#</a> 空值</h3><p><code>NULL</code>值表示没有数据。<code>NULL</code>对大小写不敏感。</p><h2 id="标识符" tabindex="-1"><a class="header-anchor" href="#标识符" aria-hidden="true">#</a> 标识符</h2><p>在 IoTDB 中，触发器名称、UDF函数名、元数据模板名称、用户与角色名等被称为标识符。</p><p>标识符命名有以下约束：</p><ul><li>在不含引用的标识符中，允许出现以下字符： <ul><li>[0-9 a-z A-Z _ : @ # $ { }] （字母，数字，部分特殊字符）</li><li>['\u2E80'..'\u9FFF'] （UNICODE 中文字符）</li></ul></li><li>标识符允许使用数字开头、允许全部为数字（<strong>不推荐！</strong>）。</li><li>标识符是大小写敏感的。</li><li>注意：用户与角色名对大小写不敏感，并且不允许转义特殊字符。</li></ul><p>如果标识符要包含不允许的特殊字符，或者使用系统关键字，需要用反引号（`）对标识符进行引用。反引号引用的标识符中出现反引号需要反斜杠转义。</p><p>示例如下：</p><div class="language-sql line-numbers-mode" data-ext="sql"><pre class="language-sql"><code>id <span class="token comment">// 合法，被解析为 id</span> |
| ID <span class="token comment">// 合法，被解析为 ID，与 id 不同</span> |
| id0 <span class="token comment">// 合法，被解析为 id0</span> |
| _id <span class="token comment">// 合法，被解析为 _id</span> |
| <span class="token number">0</span>id <span class="token comment">// 合法，被解析为 0id</span> |
| <span class="token number">233</span> <span class="token comment">// 合法，被解析为 233 (不推荐！)</span> |
| ab<span class="token operator">!</span> <span class="token comment">// 不合法，包含不被允许的特殊字符</span> |
| <span class="token identifier"><span class="token punctuation">`</span>ab!<span class="token punctuation">`</span></span> <span class="token comment">// 合法，被解析为 ab!</span> |
| <span class="token identifier"><span class="token punctuation">`</span>"ab"<span class="token punctuation">`</span></span> <span class="token comment">// 合法，被解析为 "ab"</span> |
| <span class="token identifier"><span class="token punctuation">`</span>a<span class="token punctuation">`</span></span>b<span class="token identifier"><span class="token punctuation">`</span> // 不合法，反引号应使用反斜杠进行转义 |
| <span class="token punctuation">`</span></span>a\<span class="token punctuation">`</span>b<span class="token identifier"><span class="token punctuation">`</span> // 合法，被解析为 a<span class="token punctuation">`</span></span>b |
| </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><h2 id="路径节点名" tabindex="-1"><a class="header-anchor" href="#路径节点名" aria-hidden="true">#</a> 路径节点名</h2><p>我们称一个路径中由 <code>.</code> 分割的部分叫做节点（node name）。</p><p>路径节点名的约束与标识符基本一致，但要额外注意以下几点：</p><ul><li><code>root</code> 只允许出现时间序列的开头，若其他层级出现 <code>root</code>，则无法解析，提示报错。</li><li>无论是否使用反引号引用，路径分隔符（<code>.</code>）都不能出现在路径节点名中。 如果路径节点名中一定要出现 <code>.</code> （不推荐！），需要用单引号或双引号括起。在这种情况下，为避免引发歧义，引号被系统视为节点名的一部分。</li><li>在反引号括起的路径节点名中，单引号和双引号需要使用反斜杠进行转义。</li><li>特别地，如果系统在 Windows 系统上部署，那么存储组层级名称是<strong>大小写不敏感</strong>的。例如，同时创建 <code>root.ln</code> 和 <code>root.LN</code> 是不被允许的。</li></ul><p>示例如下：</p><div class="language-sql line-numbers-mode" data-ext="sql"><pre class="language-sql"><code><span class="token keyword">CREATE</span> TIMESERIES root<span class="token punctuation">.</span>a<span class="token punctuation">.</span>b<span class="token punctuation">.</span>s1<span class="token operator">+</span>s2<span class="token operator">/</span>s3<span class="token punctuation">.</span>c <span class="token keyword">WITH</span> DATATYPE<span class="token operator">=</span>INT32<span class="token punctuation">,</span> ENCODING<span class="token operator">=</span>RLE |
| <span class="token comment">// 解析失败！</span> |
| |
| <span class="token keyword">CREATE</span> TIMESERIES root<span class="token punctuation">.</span>a<span class="token punctuation">.</span>b<span class="token punctuation">.</span><span class="token identifier"><span class="token punctuation">`</span>s1+s2/s3<span class="token punctuation">`</span></span><span class="token punctuation">.</span>c <span class="token keyword">WITH</span> DATATYPE<span class="token operator">=</span>INT32<span class="token punctuation">,</span> ENCODING<span class="token operator">=</span>RLE |
| <span class="token comment">// root.a.b.`s1+s2/s3`.c 将被解析为 Path[root, a, b, s1+s2/s3, c]</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></div><div class="language-sql line-numbers-mode" data-ext="sql"><pre class="language-sql"><code><span class="token keyword">CREATE</span> TIMESERIES root<span class="token punctuation">.</span>a<span class="token punctuation">.</span>b<span class="token punctuation">.</span><span class="token keyword">select</span> <span class="token keyword">WITH</span> DATATYPE<span class="token operator">=</span>INT32<span class="token punctuation">,</span> ENCODING<span class="token operator">=</span>RLE |
| <span class="token comment">// 解析失败！</span> |
| |
| <span class="token keyword">CREATE</span> TIMESERIES root<span class="token punctuation">.</span>a<span class="token punctuation">.</span>b<span class="token punctuation">.</span><span class="token identifier"><span class="token punctuation">`</span>select<span class="token punctuation">`</span></span> <span class="token keyword">WITH</span> DATATYPE<span class="token operator">=</span>INT32<span class="token punctuation">,</span> ENCODING<span class="token operator">=</span>RLE |
| <span class="token comment">// root.a.b.`select` 将被解析为 Path[root, a, b, select]</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></div><div class="language-sql line-numbers-mode" data-ext="sql"><pre class="language-sql"><code><span class="token keyword">CREATE</span> TIMESERIES root<span class="token punctuation">.</span>a<span class="token punctuation">.</span>b<span class="token punctuation">.</span><span class="token identifier"><span class="token punctuation">`</span>s1.s2<span class="token punctuation">`</span></span><span class="token punctuation">.</span>c <span class="token keyword">WITH</span> DATATYPE<span class="token operator">=</span>INT32<span class="token punctuation">,</span> ENCODING<span class="token operator">=</span>RLE |
| <span class="token comment">// 解析失败！</span> |
| |
| <span class="token keyword">CREATE</span> TIMESERIES root<span class="token punctuation">.</span>a<span class="token punctuation">.</span>b<span class="token punctuation">.</span><span class="token string">"s1.s2"</span><span class="token punctuation">.</span>c <span class="token keyword">WITH</span> DATATYPE<span class="token operator">=</span>INT32<span class="token punctuation">,</span> ENCODING<span class="token operator">=</span>RLE |
| <span class="token comment">// root.a.b."s1.s2".c 将被解析为 Path[root, a, b, "s1.s2", c]</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></div><div class="language-sql line-numbers-mode" data-ext="sql"><pre class="language-sql"><code><span class="token keyword">CREATE</span> TIMESERIES root<span class="token punctuation">.</span>a<span class="token punctuation">.</span>b<span class="token punctuation">.</span><span class="token identifier"><span class="token punctuation">`</span>s1"s2<span class="token punctuation">`</span></span><span class="token punctuation">.</span>c <span class="token keyword">WITH</span> DATATYPE<span class="token operator">=</span>INT32<span class="token punctuation">,</span> ENCODING<span class="token operator">=</span>RLE |
| <span class="token comment">// 解析失败！</span> |
| |
| <span class="token keyword">CREATE</span> TIMESERIES root<span class="token punctuation">.</span>a<span class="token punctuation">.</span>b<span class="token punctuation">.</span><span class="token identifier"><span class="token punctuation">`</span>s1\"s2<span class="token punctuation">`</span></span><span class="token punctuation">.</span>c <span class="token keyword">WITH</span> DATATYPE<span class="token operator">=</span>INT32<span class="token punctuation">,</span> ENCODING<span class="token operator">=</span>RLE |
| <span class="token comment">// root.a.b.`s1\"s2`.c 将被解析为 Path[root, a, b, s1\"s2, c]</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></div><h2 id="关键字和保留字" tabindex="-1"><a class="header-anchor" href="#关键字和保留字" aria-hidden="true">#</a> 关键字和保留字</h2><p>关键字是在 SQL 具有特定含义的词，不能直接用于标识符或路径节点名，需要使用反引号进行转义。保留字是关键字的一个子集，保留字不能用于标识符或路径节点名（即使进行了转义）。</p><p>关于 IoTDB 的关键字和保留字列表，可以查看 <a href="/zh/UserGuide/V0.13.x/Reference/Keywords.html" class="">关键字和保留字</a> 。</p><h2 id="表达式" tabindex="-1"><a class="header-anchor" href="#表达式" aria-hidden="true">#</a> 表达式</h2><p>IoTDB 支持在 <code>select</code> 子句中执行由数字常量、时间序列、算数运算表达式和时间序列生成函数（包括用户自定义函数）组成的任意嵌套表达式。</p><p>注意：当参与表达式的路径节点名由纯数字、单引号、或双引号组成（不推荐！）时，必须使用反引号（`）括起，以免引起歧义。示例如下：</p><div class="language-sql line-numbers-mode" data-ext="sql"><pre class="language-sql"><code><span class="token comment">-- 存在时间序列： root.sg.d.0, root.sg.d.'a' 和 root.sg."d".b</span> |
| <span class="token keyword">select</span> <span class="token number">0</span> <span class="token keyword">from</span> root<span class="token punctuation">.</span>sg<span class="token punctuation">.</span>d <span class="token comment">-- 存在歧义，解析失败</span> |
| <span class="token keyword">select</span> <span class="token string">'a'</span> <span class="token keyword">from</span> root<span class="token punctuation">.</span>sg<span class="token punctuation">.</span>d <span class="token comment">-- 存在歧义，解析失败</span> |
| <span class="token keyword">select</span> <span class="token string">"d"</span><span class="token punctuation">.</span>b <span class="token keyword">from</span> root<span class="token punctuation">.</span>sg <span class="token comment">-- 存在歧义，解析失败</span> |
| <span class="token keyword">select</span> <span class="token identifier"><span class="token punctuation">`</span>0<span class="token punctuation">`</span></span> <span class="token keyword">from</span> root<span class="token punctuation">.</span>sg<span class="token punctuation">.</span>d <span class="token comment">-- 对时间序列 root.sg.d.0 进行查询</span> |
| <span class="token keyword">select</span> <span class="token identifier"><span class="token punctuation">`</span>0<span class="token punctuation">`</span></span> <span class="token operator">+</span> <span class="token number">0</span> <span class="token keyword">from</span> root<span class="token punctuation">.</span>sg<span class="token punctuation">.</span>d <span class="token comment">-- 表达式，对时间序列 root.sg.d.0 的每一个查询结果加 0</span> |
| <span class="token keyword">select</span> myudf<span class="token punctuation">(</span><span class="token identifier"><span class="token punctuation">`</span>'a'<span class="token punctuation">`</span></span><span class="token punctuation">,</span> <span class="token string">'x'</span><span class="token punctuation">)</span> <span class="token keyword">from</span> root<span class="token punctuation">.</span>sg<span class="token punctuation">.</span>d <span class="token comment">-- 表达式，调用函数 myudf，第一个参数为时间序列 root.sg.d.'a'，第二个参数为字符串常量 'x'</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></div><h2 id="引用符号" tabindex="-1"><a class="header-anchor" href="#引用符号" aria-hidden="true">#</a> 引用符号</h2><h3 id="双引号-、单引号" tabindex="-1"><a class="header-anchor" href="#双引号-、单引号" aria-hidden="true">#</a> 双引号（"）、单引号（'）</h3><p>双引号、单引号的使用场景如下：</p><ol><li>字符串字面值由单引号或双引号括起的字符串表示。</li><li>如果要在路径节点名中使用路径分隔符（<code>.</code>），则需要将路径节点名用单引号或双引号括起。在这种情况下，为避免引发歧义，引号被系统视为节点名的一部分。</li></ol><h3 id="反引号" tabindex="-1"><a class="header-anchor" href="#反引号" aria-hidden="true">#</a> 反引号（`）</h3><p>反引号的使用场景如下：</p><ol><li>在标识符中使用特殊字符时，标识符需要使用反引号括起。</li><li>在路径节点名中使用除路径分隔符之外的特殊字符时，路径节点名需要使用反引号括起。在这种情况下，反引号不会被系统视为节点名的一部分。</li></ol><h3 id="反斜杠" tabindex="-1"><a class="header-anchor" href="#反斜杠" aria-hidden="true">#</a> 反斜杠（\）</h3><p>反斜杠的使用场景如下：</p><ul><li>在字符串常量中，出现双引号或单引号时，要使用反斜杠进行转义。 <ul><li>如："str\"ing" 解析为 str"ing、'str\'ing' 解析为 str'ing。</li></ul></li><li>在标识符中，出现反引号时，要使用反斜杠进行转义。 <ul><li>如：`na\`me` 解析为 na`me。</li></ul></li><li>在路径节点名中，出现双引号或单引号时，要使用反斜杠进行转义。注意，为了避免歧义，反斜杠会被系统视为节点名的一部分。 <ul><li>如：root.sg1.d1."a\"b" 解析为 Path[root, sg1, d1, "a\"b"]、root.sg1.d1.'a\'b' 解析为 Path[root, sg1, d1, 'a\'b']、root.sg1.d1.`a\"b` 解析为 Path[root, sg1, d1, a\"b]、root.sg1.d1.`a\'b` 解析为 Path[root, sg1, d1, a\'b]。</li></ul></li></ul><h2 id="了解更多" tabindex="-1"><a class="header-anchor" href="#了解更多" aria-hidden="true">#</a> 了解更多</h2><p>请阅读代码仓库中的词法和语法描述文件：</p><p>词法文件：<code>antlr/src/main/antlr4/org/apache/iotdb/db/qp/sql/IoTDBSqlLexer.g4</code></p><p>语法文件：<code>antlr/src/main/antlr4/org/apache/iotdb/db/qp/sql/IoTDBSqlParser.g4</code></p></div><!----><footer class="page-meta"><div class="meta-item edit-link"><a href="https://github.com/apache/iotdb/edit/rel/0.13/docs/zh/UserGuide/Reference/Syntax-Conventions.md" rel="noopener noreferrer" target="_blank" aria-label="发现错误？在 GitHub 上编辑此页" class="nav-link label"><!--[--><svg xmlns="http://www.w3.org/2000/svg" class="icon edit-icon" viewBox="0 0 1024 1024" fill="currentColor" aria-label="edit icon"><path d="M430.818 653.65a60.46 60.46 0 0 1-50.96-93.281l71.69-114.012 7.773-10.365L816.038 80.138A60.46 60.46 0 0 1 859.225 62a60.46 60.46 0 0 1 43.186 18.138l43.186 43.186a60.46 60.46 0 0 1 0 86.373L588.879 565.55l-8.637 8.637-117.466 68.234a60.46 60.46 0 0 1-31.958 11.229z"></path><path d="M728.802 962H252.891A190.883 190.883 0 0 1 62.008 771.98V296.934a190.883 190.883 0 0 1 190.883-192.61h267.754a60.46 60.46 0 0 1 0 120.92H252.891a69.962 69.962 0 0 0-69.098 69.099V771.98a69.962 69.962 0 0 0 69.098 69.098h475.911A69.962 69.962 0 0 0 797.9 771.98V503.363a60.46 60.46 0 1 1 120.922 0V771.98A190.883 190.883 0 0 1 728.802 962z"></path></svg><!--]-->发现错误？在 GitHub 上编辑此页<span><svg class="external-link-icon" xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path><polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg><span class="external-link-icon-sr-only">open in new window</span></span><!----></a></div><div class="meta-item git-info"><!----><!----></div></footer><!----><!----><!----><!--]--></main><!--]--><footer style="padding-bottom:2rem;"><span id="doc-version" style="display:none;">rel/0.13</span><p style="text-align:center;color:#909399;font-size:12px;margin:0 30px;">Copyright © 2023 The Apache Software Foundation.<br> Apache and the Apache feather logo are trademarks of The Apache Software Foundation</p><p style="text-align:center;margin-top:10px;color:#909399;font-size:12px;margin:0 30px;"><strong>Have a question?</strong> Connect with us on QQ, WeChat, or Slack. <a href="https://github.com/apache/iotdb/issues/1995">Join the community</a> now.</p><p style="text-align:center;margin-top:10px;color:#909399;font-size:12px;margin:0 30px;"> We use <a href="https://analytics.google.com">Google Analytics</a> to collect anonymous, aggregated usage information. </p></footer></div><!--]--><!--]--><!----><!--]--></div> |
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