腾讯云数据仓库 TCHouse-X CTE(Common Table Expression)

公共表表达式(CTE)定义了一个临时结果集,用户可以在 SQL 语句的范围内多次引用。CTE 主要用于 SELECT 语句。

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一、语法

WITH common_table_expression [ , … ]

其中 common_table_expression 定义为:

expression_name [ ( column_name [ , … ] ) ] [ AS ] ( query )

二、参数

子句/关键字 说明
expression_name 为公共表表达式指定名称
query 一个 SELECT 语句

三、示例

— CTE 基本用法WITH t(x, y) AS (SELECT 1, 2)SELECT * FROM t WHERE x = 1 AND y = 2– CTE 嵌套WITH t AS ( WITH t2 AS (SELECT 1) SELECT * FROM t2)SELECT * FROM t– CTE 在子查询中SELECT max(c) FROM ( WITH t(c) AS (SELECT 1) SELECT * FROM t)– CTE 在标量子查询中SELECT (WITH t AS (SELECT 1) SELECT * FROM t)– 多个 CTEWITH t1 AS (SELECT 1 AS a), t2 AS (SELECT 2 AS b)SELECT * FROM t1, t2

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