mysql if和 as 结合

SELECT CASE WHEN uid=32 THEN uid ELSE NULL END userID

CASE WHEN uid <>32 THEN uid ELSE NULL END buid

FROM `contacts` WHERE ( contacts.uid = 32 ) OR ( contacts.fuid = 32 )

IF(expr1,expr2,expr3)

如果 expr1 是TRUE (expr1 <>0 and expr1 <>NULL)，则 IF()的返回值为expr2否则返回值则为 expr3。IF() 的返回值为数字值或字符串值，具体情况视其所在语境而定。

示例：select *,if(sva=1,"男","女") as ssva from taname where sva != ""或者用case语法：

select CASE sva WHEN 1 THEN '男' ELSE '女' END as ssva from taname where sva != ''

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