8、标量子查询：select * from emp

where sal>(select avg(sal) from emp);

9、行子查询：select empno, ename,job,deptno

from emp

where (deptno,job)=(select deptno,

job from emp where ename='smith' )
and ename<>'smith';

10、子查询操作符：

not in() 在/不在其中

any 满足其中任意一个

all 都满足

11、列子查询：select * from

emp left join saligrade

on sal between lasal and hisal

where yuangongid not in (select

lingdao id from where is not null) ;

12、any操作符（任意一个): select * from emp where sal >any(select sal from emp where deptno=30) and deptno<>30;

13、all操作符： select * from emp where sal >

all(select sal from emp where deptno=30);