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  | Henry | 80000  | 2            |
| 3  | Sam   | 60000  | 2            |
| 4  | 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。例如，根据上述给定的表格，Max 在 IT 部门有最高工资，Henry 在 Sales 部门有最高工资。

+------------+----------+--------+
| Department | Employee | Salary |
+------------+----------+--------+
| IT         | Max      | 90000  |
| Sales      | Henry    | 80000  |
+------------+----------+--------+

分析

通过group by把每个部分的最高工资找出来，再通过连表，找到相应的员工名字和部门名字

代码

# Write your MySQL query statement below
SELECT
    d.Name as 'Department',
    e.Name as 'Employee',
    e.Salary
FROM
    (
        SELECT 
            DepartmentId, max(Salary) as Salary
        FROM Employee
        GROUP BY DepartmentId
     ) m ,
    Employee e,
    Department d
WHERE 
     m.DepartmentId = e.DepartmentId AND m.Salary = e.Salary AND e.DepartmentId = d.Id
;