sql当中NOT IN和IN，exists与not exists的区别

1、EXISTS=IN,意思差不多相同，但是语法上有一点不同，好像使用IN效率要差点，应该是不会执行索引的原因

SELECT ID,NAME FROM A WHERE ID IN (SELECT AID FROM B WHERE A.ID=B.AID)

SELECT ID,NAME FROM A where exists (SELECT*FROM B WHERE A.ID=B.AID)

2、NOTEXISTS=NOTIN ，意思相同不过语法上有点点区别

SELECT ID,NAME FROM A WHERE ID NOT IN (SELECT AID FROM B WHERE A.ID=B.AID)

SELECT ID,NAME FROM A WHERE　NOT exists (SELECT * FROM B WHERE A.ID=B.AID)