mysql练习题四

19、列出最低薪金大于1500的各种工作及从事此工作的全部雇员人数.

mysql> SELECT
    ->  min(sal),
    ->  job,
    ->  count(*)
    -> FROM
    ->  emp
    -> GROUP BY
    ->  job
    -> HAVING
    ->  min(sal) > 1500;
+----------+-----------+----------+
| min(sal) | job       | count(*) |
+----------+-----------+----------+
|  3000.00 | ANALYST   |        2 |
|  2450.00 | MANAGER   |        3 |
|  5000.00 | PRESIDENT |        1 |
+----------+-----------+----------+

20、列出在部门"SALES"<销售部>工作的员工的姓名,假定不知道销售部的部门编号.

mysql> SELECT
    ->  ename
    -> FROM
    ->  emp
    -> WHERE
    ->  deptno = (
    ->          SELECT
    ->                  deptno
    ->          FROM
    ->                  dept
    ->          WHERE
    ->                  dname = 'SALES'
    ->  );
+--------+
| ename  |
+--------+
| ALLEN  |
| WARD   |
| MARTIN |
| BLAKE  |
| TURNER |
| JAMES  |
+--------+

21、列出薪金高于公司平均薪金的所有员工,所在部门,上级领导,雇员的工资等级.

mysql> SELECT
    ->  e.ename as empname, d.dname, s.grade, b.ename as leadername
    -> FROM
    ->  emp e
    -> JOIN
    ->  salgrade s
    -> ON
    ->  e.sal BETWEEN s.losal AND s.hisal
    -> join
    ->  dept d
    -> on
    ->  d.DEPTNO = e.DEPTNO
    -> left join
    ->  emp b
    -> on
    ->  e.mgr = b.empno
    -> WHERE
    ->  e.sal > (SELECT avg(sal) FROM emp);
+---------+------------+-------+------------+
| empname | dname      | grade | leadername |
+---------+------------+-------+------------+
| JONES   | RESEARCH   |     4 | KING       |
| BLAKE   | SALES      |     4 | KING       |
| CLARK   | ACCOUNTING |     4 | KING       |
| SCOTT   | RESEARCH   |     4 | JONES      |
| FORD    | RESEARCH   |     4 | JONES      |
| KING    | ACCOUNTING |     5 | NULL       |
+---------+------------+-------+------------+

22、列出与"SCOTT"从事相同工作的所有员工及部门名称.

mysql> SELECT
    ->  e.ename,
    ->  e.job,
    ->  d.dname
    -> FROM
    ->  emp e
    -> JOIN
    ->  dept d
    -> ON
    ->  e.deptno = d.deptno
    -> WHERE
    ->  e.job = (
    ->          SELECT
    ->                  job
    ->          FROM
    ->                  emp
    ->          WHERE
    ->                  ename = 'SCOTT'
    ->  );
+-------+---------+----------+
| ename | job     | dname    |
+-------+---------+----------+
| SCOTT | ANALYST | RESEARCH |
| FORD  | ANALYST | RESEARCH |
+-------+---------+----------+

23、列出薪金等于部门30中员工的薪金的其他员工的姓名和薪金.

mysql> SELECT
    ->  ename,
    ->  sal
    -> FROM
    ->  emp
    -> WHERE
    ->  sal IN (
    ->          SELECT DISTINCT
    ->                  sal
    ->          FROM
    ->                  emp
    ->          WHERE
    ->                  deptno = 30
    ->  )
    -> AND
    ->  deptno != 30;
Empty set (0.00 sec)

24、列出薪金高于在部门30工作的所有员工的薪金的员工姓名和薪金.部门名称.

mysql> SELECT
    ->  e.ename,
    ->  e.sal,
    ->  d.dname
    -> FROM
    ->  emp e
    -> JOIN
    ->  dept d
    -> ON
    ->  e.deptno = d.deptno
    -> WHERE
    ->  sal > (
    ->          SELECT
    ->                  max(sal)
    ->          FROM
    ->                  emp
    ->          WHERE
    ->                  deptno = 30
    ->  );
+-------+---------+------------+
| ename | sal     | dname      |
+-------+---------+------------+
| KING  | 5000.00 | ACCOUNTING |
| JONES | 2975.00 | RESEARCH   |
| SCOTT | 3000.00 | RESEARCH   |
| FORD  | 3000.00 | RESEARCH   |
+-------+---------+------------+

25、列出在每个部门工作的员工数量,平均工资和平均服务期限.

mysql> SELECT
    ->     d.deptno,
    ->     count(e.ename) as totalemp,
    ->     ifnull(avg(e.sal), 0) as avgsal,
    ->     ifnull(avg((to_days(now())-to_days(hiredate))/365), 0) as avgtime
    -> FROM
    ->     dept d
    -> LEFT outer JOIN
    ->     emp e
    -> on
    ->     d.deptno = e.deptno
    -> group by
    ->     d.deptno;
+--------+----------+-------------+-------------+
| deptno | totalemp | avgsal      | avgtime     |
+--------+----------+-------------+-------------+
|     10 |        3 | 2916.666667 | 35.37625571 |
|     20 |        5 | 2175.000000 | 34.60383562 |
|     30 |        6 | 1566.666667 | 35.67488584 |
|     40 |        0 |    0.000000 |  0.00000000 |
+--------+----------+-------------+-------------+

to_days()函数的运用。