[英]How to use case statement in MySQL
我正在使用where条件的mysql语句中使用三个查询,例如如何将其作为单个查询
SELECT COUNT(*) as A FROM tbl_user WHERE (b=1 AND c=0) AND (d=1 AND e=1)
SELECT COUNT(*) as M FROM tbl_user WHERE (H=1 AND I=0) AND (J=1 AND K=1)
SELECT
sum(case when (b=1 AND c=0) AND (d=1 AND e=1) then 1 else 0 end) as CountA,
sum(case when (H=1 AND I=0) AND (J=1 AND K=1) then 1 else 0 end) as CountM
FROM tbl_user
你并不需要一个CASE
语句来做到这一点(虽然它可能会在一定程度上更容易比使用阅读IF
如果包含了条件OR
S),其目的是用更好的输送IF
:
SELECT SUM(IF(b=1 AND c=0 AND d=1 AND e=1, 1, 0)) AS A,
SUM(IF(H=1 AND I=0 AND J=1 AND K=1, 1, 0)) AS M
FROM tbl_user
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