如何在MySQL中使用case语句

Question

i am using three query's in mysql statement using where condition for example,how to make this as a single query

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)

Answer 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 

Answer 2

You don't need a CASE statement to do this (although it'd possibly be somewhat easier to read than using IF if the conditions contained OR s), the intent is better conveyed with an 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