Orcla 数据库复习2 --子查询和表连接

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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)

)