赋值操作符(:=)

语法

var_name := expr

描述

该赋值操作符用于为一个变量进行赋值。操作符右边的值将赋值给操作符左边的变量。

不像=操作符,:=操作符总是可以用来为变量赋值。(译者注:使用select语句赋值时不能使用"="进行赋值)。

该操作符可以为用户自定义变量user-defined variables和本地变量local variables赋值。

当要为多个变量赋值相同的值时,可以考虑使用LAST_VALUE()函数。

示例

 SELECT @x := 10;
+----------+
| @x := 10 |
+----------+
|       10 |
+----------+

SELECT @x, @y := @x;
+------+----------+
| @x   | @y := @x |
+------+----------+
|   10 |       10 |
+------+----------+

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