Question

给出一个表Employees

+-------+--------+-----------+------+-----------+------+------+--------+
| EMPNO | ENAME  |    JOB    | MGR  | HIREDATE  | SAL  | COMM | DEPTNO |
+-------+--------+-----------+------+-----------+------+------+--------+
|  7369 | SMITH  | CLERK     | 7902 | 17-Dec-80 |  800 |      |     20 |
|  7499 | ALLEN  | SALESMAN  | 7698 | 20-Feb-81 | 1600 |  300 |     30 |
|  7521 | WARD   | SALESMAN  | 7698 | 22-Feb-81 | 1250 |  500 |     30 |
|  7566 | JONES  | MANAGER   | 7839 | 02-Apr-81 | 2975 |      |     20 |
|  7654 | MARTIN | SALESMAN  | 7698 | 28-Sep-81 | 1250 | 1400 |     30 |
|  7698 | BLAKE  | MANAGER   | 7839 | 01-May-81 | 2850 |      |     30 |
|  7782 | CLARK  | MANAGER   | 7839 | 09-Jun-81 | 2450 |      |     10 |
|  7788 | SCOTT  | ANALYST   | 7566 | 19-Apr-87 | 3000 |      |     20 |
|  7839 | KING   | PRESIDENT | null | 17-Nov-81 | 5000 |      |     10 |
|  7844 | TURNER | SALESMAN  | 7698 | 08-Sep-81 | 1500 |    0 |     30 |
|  7876 | ADAMS  | CLERK     | 7788 | 23-May-87 | 1100 |      |     20 |
|  7900 | JAMES  | CLERK     | 7698 | 03-Dec-81 |  950 |      |     30 |
|  7902 | FORD   | ANALYST   | 7566 | 03-Dec-81 | 3000 |      |     20 |
|  7934 | MILLER | CLERK     | 7782 | 23-Jan-82 | 1300 |      |     10 |
+-------+--------+-----------+------+-----------+------+------+--------+

另一张表Departments

+--------+------------+----------+
| DEPTNO |   DNAME    |   LOC    |
+--------+------------+----------+
|     10 | ACCOUNTING | NEW YORK |
|     20 | RESEARCH   | DALLAS   |
|     30 | SALES      | CHICAGO  |
|     40 | OPERATIONS | BOSTON   |
+--------+------------+----------+

如何找到每个部门的最高工资？

输出格式行为：

DEPTNO,ENAME,DNAME,SAL,LOC

Answer 1

如果您想与员工一起找到最高薪水，请使用ANSI标准row_number()功能：

select d.deptno, e.ename, d.dname, e.sal, d.loc
from (select e.*, row_number() over (partition by deptno order by sal desc) as seqnum
      from employees e
     ) e join
     departments d
     on e.deptno = d.deptno
where seqnum = 1

SQL Fiddle

Answer 2

您可以使用将为每个部门获取max(salary)的子查询：

select de.deptno,
  e.ename,
  de.dname,
  e.sal,
  de.loc
from employees e
inner join
(
  select max(e.sal) MaxSalary, d.deptno, d.loc, d.dname
  from employees e
  inner join departments d
     on e.deptno = d.deptno
  group by d.deptno, d.loc, d.dname
) de
  on e.sal = de.MaxSalary
  and e.deptno = de.deptno
order by de.deptno

见SQL Fiddle with Demo。您会注意到这会为deptno=20返回2行，因为有两个员工具有相同的薪水。

如果您使用的是具有窗口功能的数据库，那么您将需要使用dense_rank()，这样您将返回所有在每个部门拥有最高薪水的员工：

select d.deptno, e.ename, d.dname, e.sal, d.loc
from 
(
  select e.ename,
    e.sal, 
    e.deptno,
    dense_rank() over (partition by deptno order by sal desc) as salRank
  from employees e
) e 
inner join departments d
  on e.deptno = d.deptno
where salRank = 1;

见SQL Fiddle with Demo。

两个版本的结果是：

| DEPTNO | ENAME |      DNAME |  SAL |      LOC |
-------------------------------------------------
|     10 |  KING | ACCOUNTING | 5000 | NEW YORK |
|     20 | SCOTT |   RESEARCH | 3000 |   DALLAS |
|     20 |  FORD |   RESEARCH | 3000 |   DALLAS |
|     30 | BLAKE |      SALES | 2850 |  CHICAGO |

如何选择每个部门的最高工资，包括获得该部门的员工

2 个答案: