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  • 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


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  • 原文地址:https://www.cnblogs.com/yxysuanfa/p/6774082.html
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