3列出个个部门的平均工资显示部门名称

(3)列出个个部门的平均工资显示部门名称，平均工资

select d.dname,round(avg(e.salary)) asal from emp_yang e join dept_yang d on e.deptno=d.deptno group by d.dname

select max(d.dname),round(avg(e.salary)) asal from emp_yang e join dept_yang d on e.deptno=d.deptno group by d.deptno

在from

(4)那些员工的工资比本部门的平均工资高

select e.ename,round(avg(e.salary)) from emp_yang e join (select deptno,round(avg(salary)) asal from emp_yang group by deptno) a on e.deptno =a.deptno and e.salary>a.asal

自连接

(5)列出员工的名字和领导的名字

select t1.ename employee,decode(t2.ename,t1.ename,'boss',t2.ename) manager from emp_yang t1 join emp_yang t2 on nvl(t1.mgr,t1.empno)=t2.empno