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