【LeetCode】184. 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  |

+------------+----------+--------+

刚开始不知道咋想的，想着两个表先联一下，然后对id group by，好像想乱了，吃饭回来发现其实两个表联一下，只要ID相等，然后找最大的薪水就行了，语句如下：

select b.Name as Department ,a.Name as Employee ,a.Salary as Salary from Employee a,Department b where a.DepartmentId=b.Id
and a.Salary=(select max(Salary) from Employee where DepartmentId=b.Id)