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| --- | ||
| title: 表达式语法 | ||
| summary: 本文列出 TiDB 的表达式语法。 | ||
| category: reference | ||
| aliases: ['/docs-cn/dev/reference/sql/language-structure/expression-syntax/'] | ||
| --- | ||
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| # 表达式语法 (Expression Syntax) | ||
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| 在 TiDB 中，以下规则是表达式的语法，你可以在 `parser/parser.y` 中找到定义。TiDB 的语法解析是基于 yacc 的。 | ||
| 表达式是一个或多个值、操作符或函数的组合。在 TiDB 中，表达式主要使用在 `SELECT` 语句的各个子句中，包括 Group by 子句、Where 子句、Having 子句、Join 条件以及窗口函数等。此外，部分 DDL 语句也会使用到表达式，例如建表时默认值的设置、生成列的设置，分区规则等。 | ||
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| ``` | ||
| Expression: | ||
| singleAtIdentifier assignmentEq Expression | ||
| | Expression logOr Expression | ||
| | Expression "XOR" Expression | ||
| | Expression logAnd Expression | ||
| | "NOT" Expression | ||
| | Factor IsOrNotOp trueKwd | ||
| | Factor IsOrNotOp falseKwd | ||
| | Factor IsOrNotOp "UNKNOWN" | ||
| | Factor | ||
| 表达式包含几种类型： | ||
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| Factor: | ||
| Factor IsOrNotOp "NULL" | ||
| | Factor CompareOp PredicateExpr | ||
| | Factor CompareOp singleAtIdentifier assignmentEq PredicateExpr | ||
| | Factor CompareOp AnyOrAll SubSelect | ||
| | PredicateExpr | ||
| + 标识符，可参考[模式对象名](/schema-object-names.md)。 | ||
| + 谓词、数值、字符串、日期表达式等，这些类型的[字面值](/literal-values.md)也是表达式。 | ||
| + 函数调用，窗口函数等。可参考[函数和操作符概述](/functions-and-operators/functions-and-operators-overview.md) 和 [窗口函数](/functions-and-operators/window-functions.md)。 | ||
| + 其他，包括 paramMarker（即 `?`）、系统变量和用户变量、CASE 表达式等。 | ||
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| PredicateExpr: | ||
| PrimaryFactor InOrNotOp '(' ExpressionList ')' | ||
| | PrimaryFactor InOrNotOp SubSelect | ||
| | PrimaryFactor BetweenOrNotOp PrimaryFactor "AND" PredicateExpr | ||
| | PrimaryFactor LikeOrNotOp PrimaryExpression LikeEscapeOpt | ||
| | PrimaryFactor RegexpOrNotOp PrimaryExpression | ||
| | PrimaryFactor | ||
| 以下规则是表达式的语法，该语法基于 TiDB parser 的 [parser.y](https://github.com/pingcap/parser/blob/master/parser.y) 文件中所定义的规则。此外，下列语法图的可导航版本请参考 [TiDB SQL 语法图](https://pingcap.github.io/sqlgram/#Expression)。 | ||
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| PrimaryFactor: | ||
| PrimaryFactor '|' PrimaryFactor | ||
| | PrimaryFactor '&' PrimaryFactor | ||
| | PrimaryFactor "<<" PrimaryFactor | ||
| | PrimaryFactor ">>" PrimaryFactor | ||
| | PrimaryFactor '+' PrimaryFactor | ||
| | PrimaryFactor '-' PrimaryFactor | ||
| | PrimaryFactor '*' PrimaryFactor | ||
| | PrimaryFactor '/' PrimaryFactor | ||
| | PrimaryFactor '%' PrimaryFactor | ||
| | PrimaryFactor "DIV" PrimaryFactor | ||
| | PrimaryFactor "MOD" PrimaryFactor | ||
| | PrimaryFactor '^' PrimaryFactor | ||
| | PrimaryExpression | ||
| **Expression:** | ||
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| PrimaryExpression: | ||
| Operand | ||
| | FunctionCallKeyword | ||
| | FunctionCallNonKeyword | ||
| | FunctionCallAgg | ||
| | FunctionCallGeneric | ||
| | Identifier jss stringLit | ||
| | Identifier juss stringLit | ||
| | SubSelect | ||
| | '!' PrimaryExpression | ||
| | '~' PrimaryExpression | ||
| | '-' PrimaryExpression | ||
| | '+' PrimaryExpression | ||
| | "BINARY" PrimaryExpression | ||
| | PrimaryExpression "COLLATE" StringName | ||
| ``` | ||
|  | ||
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| **PredicateExpr:** | ||
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| **BitExpr:** | ||
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| **SimpleExpr:** | ||
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