如何選擇每個部門的最高薪水，其中包括賺取了

Question

給定一個表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 | 
+-------+--------+-----------+------+-----------+------+------+--------+ 

而另一臺Departments

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

我如何才能找到每個部門的最高薪水的員工？

輸出格式線：

DEPTNO,ENAME,DNAME,SAL,LOC 

Answer 1

如果你想找到薪與員工一起，然後使用ANSI標準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

您可以使用子查詢將獲得每個部門的max(salary)：

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 

請參閱SQL Fiddle with Demo。你會注意到這返回2行deptno=20，因爲有兩個僱員有相同的工資。

如果您使用的是已經窗函數的數據庫，那麼你將要使用dense_rank()，那麼你將返回誰擁有最大的薪金在各部門的所有員工：

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; 

見SQL Fiddle with Demo。

兩個版本的結果是：

| 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 |