leetcode中的SQL题(八)

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

解析：
把两个匹配的行内关联起来。

答案:

select b.name Department , a.Name  Employee, a.Salary Salary 
from Employee a inner join Department b
on a.DepartmentId = b.Id 
where a.Salary = 
(select max(Salary) from Employee where DepartmentId = b.id);