ORACLE EXSIST 练习
exists (sql 返回结果集为真)
notexists (sql 不返回结果集为真)
如下:
表A
表B
表A和表B是1对多的关系 A.ID => B.AID
select a.id from A where exists (select a.id from b where a.id = b.aid);
select a.id from A where not exists ( select a.id from b where a.id = b.aid );
条件查询
select * from A where exists (select a.id from b where a.id = b.aid and b.name != 'b3');
select a.id from A where not exists (select a.id from b where a.id = b.aid and b.name != 'b3');
三个表联合exist
母表
子表
又子表
查询语句
select name from C
where exists (
select * from b where b.id = c.bid and exists (
select * from a where a.id = b.aid
)
);
查询结果