查詢員工信息：職位與7566員工一樣，薪水大于7782員工的薪水 單行
select *
from emp
where job=(select job from emp where empno=7566) and
sal>(select sal from emp where empno=7782)
相關子查詢，員工sal大于本部門sal
select rownum,empno,ename,sal,(select avg(sal) from emp where deptno=e.deptno ) avgsal
from emp e
where sal>(select avg(sal) from emp where deptno=e.deptno)
