有一张员工表，有员工名称，部门编号，工资收入，查询每个部门中收入前三的人员清

select t1.deptno,t2.dName,t1.ename,t1.sal from

(

select deptno,ename,sal

from (select deptno,ename,sal,row_number() over(partition by deptno order by sal)rn

from emp) 

where rn <=3) t1 left join dept t2 on t2.deptno=t1.deptno