求部門平均薪水的等級

• A.求部門平均薪水的等級。

select deptno,avg_sal,grade from
(select deptno,avg(sal) avg_sal from emp group by deptno)t
join salgrade s on(t.avg_sal between s.losal and s.hisal)

• B.求部門平均的薪水等級

select deptno,avg(grade) from
(select deptno,ename, grade from emp join salgrade s on(emp.sal between s.losal and
s.hisal)) t
group by deptno

• C.那些人是經理

select ename from emp where empno in(select mgr from emp);
select ename from emp where empno in(select distinct mgr from emp);

• D.不準用組函數，求薪水的最高值（面試題）

select distinct sal from emp where sal not in(
select distinct e1.sal from emp e1 join emp e2 on (e1.sal<e2.sal));

• E.平均薪水最高的部門編號

select deptno,avg_sal from
(select avg(sal)avg_sal,deptno from emp group by deptno)
where avg_sal=
(select max(avg_sal)from
(select avg(sal) avg_sal,deptno from emp group by deptno)
)

• F.平均薪水最高的部門名稱

select dname from dept where deptno=
(
select deptno from
(select avg(sal)avg_sal,deptno from emp group by deptno)
where avg_sal=
(select max(avg_sal)from
(select avg(sal) avg_sal,deptno from emp group by deptno)
)
)

• G.求平均薪水的等級最低的部門的部門名稱

組函數嵌套
如：平均薪水最高的部門編號，可以E.更簡單的方法如下：
select deptno,avg_sal from
(select avg(sal) avg_sal,deptno from emp group by deptno)
where avg_sal =
(select max(avg(sal)) from emp group by deptno)

?

組函數最多嵌套兩層

分析：
首先求
1.平均薪水： select avg(sal) from group by deptno;

2.平均薪水等級： 把平均薪水當做一張表，需要和另外一張表連接salgrade
select deptno,grade avg_sal from
( select deptno,avg(sal) avg_sal from emp group by deptno) t
join salgrade s on(t.avg_sal between s.losal and s.hisal)

上面結果又可當成一張表。

DEPTNO GRADE AVG_SAL
-------- ------- ----------
30 3 1566.66667
20 4 2175
10 4 2916.66667

3.求上表平均等級最低值

select min(grade) from
(
select deptno,grade,avg_sal from
(select deptno,avg(sal) avg_sal from emp group by deptno)t
join salgrade s on(t.avg_sal between s.losal and s.hisa)
)

4.把最低值對應的2結果的那張表的對應那張表的deptno, 然后把2對應的表和另外一張表做連接。

select dname ,deptno,grade,avg_sal from
(
select deptno,grade,avg_sal from
(select deptno,avg(sal) avg_sal from emp group by deptno)t
join salgrade s on(t.avg_sal between s.losal and s.hisal)
) t1
join dept on (t1.deptno = dept.deptno)
where t1.grade =
(
select deptno,grade,avg_sal from
(select deptno,avg(sal) avg_sal from emp group by deptno) t
join salgrade s on(t.avg_sal between s.losal and s.hisal)
)
)
結果如下：

DNAME DEPTNO GRADE AVG_SAL
-------- ------- -------- --------
SALES 30 3 1566.6667

• H: 視圖（視圖就是一張表，一個字查詢）

G中語句有重復，可以用視圖來簡化。
conn sys/bjsxt as sysdba;
grant create table,create view to scott;
conn scott/tiger
創建視圖：
create view v$_dept_avg-sal_info as
select deptno,grade,avg_sal from
( select deptno,avg(sal) avg_sal from emp group by deptno)t
join salgrade s on 9t.avg_sal between s.losal and s.hisal)

然后
select * from v$_dept_avg-sal_info

結果如下：
DEPTNO GRADE AVG_SAL
-------- ------- ----------
30 3 1566.66667
20 4 2175
10 4 2916.66667

然后G中查詢可以簡化成：
select dname,t1.deptno,grade,avg_sal from
v$_dept_avg-sal_info t1
join dept on9t1.deptno =dept.deptno)
where t1.grade=
(
select min(grade) from v$_dept_avg-sal_info t1
)

總結

以上是生活随笔為你收集整理的Oracle学习五的全部內容，希望文章能夠幫你解決所遇到的問題。

如果覺得生活随笔網站內容還不錯，歡迎將生活随笔推薦給好友。