Mysql使用SELECT CASE的结果存储变量

Question

我正在学习如何使用SELECT CASE，但我不太了解，这里是代码：

SET @vgls=1;
SET @lgls=1;


SET @st=SELECT CASE 
WHEN @vgls=@lgls THEN "emp"
WHEN @vgls>@lgls THEN "loc"
WHEN @vgls<@lgls THEN "vis" END;

SELECT @st;

它给了我以下错误：

[Err] 1064 - You have an error in your SQL syntax; check the manual that corresponds to you  MySQL server version for the right syntax to use near 'SELECT CASE 
WHEN @vgls=@lgls THEN "emp"
WHEN @vgls>@lgls THEN "loc"
WHEN @vg' at line 1

Answer 1

您需要使用SELECT ... INTO

SELECT
...
INTO var_name [, var_name]]

而不是set将SELECT的结果赋给变量。所以这应该这样做：

SELECT CASE 
WHEN @vgls=@lgls THEN "emp"
WHEN @vgls>@lgls THEN "loc"
WHEN @vgls<@lgls THEN "vis" END
INTO @st;