没有明白 select sum(if(ShowStatus =1,1,0)) as ShowCount, sum(if(ShowStatus =3,1,0)) as HideCount FROM t_C
因为 t_A 和 t_B 是一对多的关系 t_B 和 t_C是一对多的关系。 我想查处 t_A 对应t_B 对应t_C的那些状态的数量 就是把上面那个放到下面做联合查询里 SELECT a.ID as AID,a.UserName,b.ID as BID, b.ContentNotes,c.ShowCount,C.HideCount FROM t_A a LEFT JOIN t_B b ON a.ID = b.AID LEFT JOIN t_C c On b.ID = c.BID
SELECT a.ID as AID,a.UserName,b.ID as BID, b.ContentNotes,c.ShowCount,C.HideCount FROM t_A a LEFT JOIN t_B b ON a.ID = b.AID LEFT JOIN (select sum(if(ShowStatus =1,1,0)) as ShowCount, sum(if(ShowStatus =3,1,0)) as HideCount FROM t_C group by ID) c On b.ID = c.BID
SELECT a.ID as AID,a.UserName,b.ID as BID, b.ContentNotes,c.ShowCount,C.HideCount FROM t_A a LEFT JOIN t_B b ON a.ID = b.AID LEFT JOIN (select sum(if(ShowStatus =1,1,0)) as ShowCount, sum(if(ShowStatus =3,1,0)) as HideCount, ID FROM t_C group by ID) c On b.ID = c.BID
select sum(if(ShowStatus =1,1,0)) as ShowCount,
sum(if(ShowStatus =3,1,0)) as HideCount
FROM t_C
t_B 和 t_C是一对多的关系。
我想查处 t_A 对应t_B 对应t_C的那些状态的数量
就是把上面那个放到下面做联合查询里
SELECT a.ID as AID,a.UserName,b.ID as BID, b.ContentNotes,c.ShowCount,C.HideCount FROM t_A a
LEFT JOIN t_B b ON a.ID = b.AID
LEFT JOIN t_C c On b.ID = c.BID
SELECT a.ID as AID,a.UserName,b.ID as BID, b.ContentNotes,c.ShowCount,C.HideCount FROM t_A a
LEFT JOIN t_B b ON a.ID = b.AID
LEFT JOIN (select sum(if(ShowStatus =1,1,0)) as ShowCount,
sum(if(ShowStatus =3,1,0)) as HideCount
FROM t_C group by ID) c On b.ID = c.BID
SELECT a.ID as AID,a.UserName,b.ID as BID, b.ContentNotes,c.ShowCount,C.HideCount FROM t_A a
LEFT JOIN t_B b ON a.ID = b.AID
LEFT JOIN (select sum(if(ShowStatus =1,1,0)) as ShowCount,
sum(if(ShowStatus =3,1,0)) as HideCount, ID
FROM t_C group by ID) c On b.ID = c.BID