如何简化多个“不在”查询?使用多个子查询是否有效:不在(...),不在(..)和不在(..)
我正在使用count(对不起,忘了这一点)
Select count (VisitorID)
from Company
where VisitorID not in (select VisitorID from UserLog where ActionID = 2 )
and VisitorID not in (select VisitorID from Supplies where productID = 4)
最佳答案
Select count (VisitorID)
from Company C
where
NOT EXISTS (select * from UserLog U where ActionID = 2 AND C.VisitorID = U.VisitorID)
AND
NOT EXISTS (select * from Supplies S where productID = 4 AND S.VisitorID = U.VisitorID)
为什么不存在?
通常,不存在是唯一正确的选择
关于sql - 对多个表使用NOT IN,我们在Stack Overflow上找到一个类似的问题:https://stackoverflow.com/questions/3805153/