一、题目描述
Employee
表包含所有员工信息,每个员工有其对应的 Id, salary 和 department Id。
+----+-------+--------+--------------+
| Id | Name | Salary | DepartmentId |
+----+-------+--------+--------------+
| 1 | Joe | 70000 | 1 |
| 2 | Jim | 90000 | 1 |
| 3 | Henry | 80000 | 2 |
| 4 | Sam | 60000 | 2 |
| 5 | Max | 90000 | 1 |
+----+-------+--------+--------------+
Department
表包含公司所有部门的信息。
+----+----------+
| Id | Name |
+----+----------+
| 1 | IT |
| 2 | Sales |
+----+----------+
编写一个 SQL 查询,找出每个部门工资最高的员工。对于上述表,您的 SQL 查询应返回以下行(行的顺序无关紧要)。
+------------+----------+--------+
| Department | Employee | Salary |
+------------+----------+--------+
| IT | Max | 90000 |
| IT | Jim | 90000 |
| Sales | Henry | 80000 |
+------------+----------+--------+
解释:
Max 和 Jim 在 IT 部门的工资都是最高的,Henry 在销售部的工资最高。
二、解题思路
使用DENSE_RANK连续排名函数
SQL四大排名函数(ROW_NUMBER、RANK、DENSE_RANK、NTILE)
三、代码
select Department,Employee,Salary
from(
select b.name Department,a.Name Employee,Salary,dense_rank()over(partition by b.name order by Salary desc) as row_num
from Employee a
inner join Department b on a.DepartmentId=b.Id
)a
where row_num=1