Orcla 数据库复习2 --子查询和表连接

子查询和表连接

 ①.查询挣钱最多的人的名字

 SELECT ename,sal FROM emp

 WHERE sal=(SELECT MAX(sal) FROM emp);

 ②.查询有哪些人的工资位于全部人的平均工资之上

 SELECT ename,sal FROM emp

 WHERE sal > (SELECT AVG(sal) FROM emp);

 ③.求部门中哪些人的薪水最高:

 SELECT ename,sal FROM emp

 JOIN (SELECT MAX(sal) max_sal,deptno FROM emp GROUP BY deptno) t

 ON emp.sal =t.max_sal AND emp.deptno = t.deptno;

④.求出员工的名字和他的经理人姓名

  SELECT  e1.ename, e2.ename FROM

  emp e1 JOIN emp e2

  ON e1.mgr = e2.empno;

 ⑤.查询出每一个人的薪水等级

  SELECT ename,grade FROM emp e JOIN salgrade s

  ON  (e.sal BETWEEN s.losal AND s.hisal);

 ⑥查询出每一个人的部门名称和薪水等级

 SELECT ename,dname,grade FROM

 emp e JOIN dept d ON (e.deptno =d.deptno)

 JOIN salgrade s ON (e.sal BETWEEN s.losal AND s.hisal)

 ⑦(左外连接) 查询出雇员的名字和他经理人的名字

 SELECT e1.ename, e2.ename FROM

 emp e1 LEFT JOIN emp e2

 ON e1.mgr = e2.empno;

⑧(右外连接) 查询出全部雇员的部门名称

 SELECT ename ,dname FROM

 emp e RIGHT JOIN dept d

 ON e.deptno = d.deptno;

 ⑨(全外连接) 查询出全部雇员的部门名称

 SELECT ename ,dname FROM

 emp e FULL JOIN dept d

 ON e.deptno = d.deptno;

 ⑩求部门平均薪水的等级

 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;

--求部门平均的薪水等级

  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;

--求雇员中哪些人是经理人

 SELECT  ename FROM emp

 WHERE  empno  in(SELECT DISTINCT mgr FROM emp);

--不准用组函数,求薪水的最高值

  SELECT sal FROM emp WHERE sal NOT IN

 (SELECT DISTINCT  e1.sal FROM emp e1  JOIN  emp e2

 ON e1.sal< e2.sal);

--平均薪水最高的部门的部门编号

SELECT deptno ,avg_sal FROM

( SELECT deptno, AVG(sal) avg_sal FROM emp GROUP BY deptno);

WHERE avg_sal =

(SELECT MAX(avg_sal) FROM

( SELECT deptno, AVG(sal) avg_sal FROM emp GROUP BY deptno));

--平均薪水最高的部门的部门名称

SELECT dname FROM dept WHERE deptno =

(SELECT deptno  FROM

        ( SELECT deptno, AVG(sal) avg_sal FROM emp GROUP BY deptno)

 WHERE avg_sal =

(SELECT MAX(avg_sal) FROM

        ( SELECT deptno, AVG(sal) avg_sal FROM emp GROUP BY deptno)

  )

);



--求平均薪水的等级最低的部门的部门名称

SELECT dept.dname,t1.deptno,grade,avg_sal FROM

(

SELECT deptno,grade,avg_sal FROM

(SELECT AVG(sal) avg_sal, deptno 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 MIN(grade) FROM

(SELECT deptno,grade,avg_sal FROM

(SELECT AVG(sal) avg_sal, deptno FROM emp GROUP BY deptno) t JOIN salgrade s

ON t.avg_sal BETWEEN s.losal AND s.hisal))



--求部门经理人平均薪水最低的部门名称





--求比普通员工的最高薪水还要高的经理人名称

  SELECT ename  FROM emp WHERE

  empno IN (SELECT DISTINCT mgr FROM emp WHERE mgr IS NOT NULL)

  AND sal >

(SELECT max(sal) FROM  emp WHERE empno NOT  IN

(SELECT DISTINCT mgr FROM emp WHERE mgr IS NOT NULL))



--求薪水最高的前5名雇员

SELECT ename,sal

FROM (

SELECT ename,sal FROM emp ORDER BY sal DESC

)

WHERE ROWNUM <=5;

--求薪水最高的第6到第10名雇员

SELECT ename,sal FROM(

SELECT ename,sal, ROWNUM r FROM(

SELECT ename,sal FROM emp ORDER BY sal DESC)

)

WHERE r>=6 AND r<=10;

注:查询语句是自己看马士兵的视频敲出来的