Leetcode刷SQL 2、部门工资最高的员工

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  |
+------------+----------+--------+

本题存在以下几个麻烦点：
1、按照部门分类查询工资最高的
2、可能存在多个人会有相同的最高工资
3、部门和员工不对应（这点值得吐槽）

SELECT
  d.Name AS Department,
  e2.Name AS Employee,
  e2.Salary AS Salary
FROM
  Department d
  LEFT JOIN employee e2
    ON e2.departmentId = d.id
  RIGHT JOIN
    (SELECT
      e.DepartmentId,
      MAX(e.`Salary`) AS salary
    FROM
      employee e
    GROUP BY e.`DepartmentId`) e1 //查询最高薪水
    ON e1.Salary = e2.`Salary`
    AND e1.DepartmentId = e2.`DepartmentId`
WHERE e2.id IS NOT NULL