not in 和 not exists 区别

select * from TableA a where not exists (select b.AId from TableB b where b.AId=a.id)等价

select * from TableA a where a.id not in(select b.AId from TableB b where b.AId is not null and b.AId !='')

注意：

如果去掉红色部分约束条件，当查询集合（select b.AId from TableB b）中没有null和空字符串时，

select * from TableA a where a.id not in(select b.AId from TableB b）查询结果正确

若查询集合（select b.AId from TableB b）中 有null或空字符串时
，

select * from TableA a where a.id not in(select b.AId from TableB b）查询结果为null