【LeetCode-SQL高手挑战】—185. 部门工资前三高的所有员工

表: Employee
+--------------+---------+
| Column Name  | Type    |
+--------------+---------+
| id           | int     |
| name         | varchar |
| salary       | int     |
| departmentId | int     |
+--------------+---------+
Id是该表的主键列。
departmentId是Department表中ID的外键。
该表的每一行都表示员工的ID、姓名和工资。它还包含了他们部门的ID。
表: Department
+-------------+---------+
| Column Name | Type    |
+-------------+---------+
| id          | int     |
| name        | varchar |
+-------------+---------+
Id是该表的主键列。
该表的每一行表示部门ID和部门名。

🚩查询结果如下例所示
输入: 
Employee 表:
+----+-------+--------+--------------+
| id | name  | salary | departmentId |
+----+-------+--------+--------------+
| 1  | Joe   | 85000  | 1            |
| 2  | Henry | 80000  | 2            |
| 3  | Sam   | 60000  | 2            |
| 4  | Max   | 90000  | 1            |
| 5  | Janet | 69000  | 1            |
| 6  | Randy | 85000  | 1            |
| 7  | Will  | 70000  | 1            |
+----+-------+--------+--------------+
Department  表:
+----+-------+
| id | name  |
+----+-------+
| 1  | IT    |
| 2  | Sales |
+----+-------+
输出: 
+------------+----------+--------+
| Department | Employee | Salary |
+------------+----------+--------+
| IT         | Max      | 90000  |
| IT         | Joe      | 85000  |
| IT         | Randy    | 85000  |
| IT         | Will     | 70000  |
| Sales      | Henry    | 80000  |
| Sales      | Sam      | 60000  |
+------------+----------+--------+
解释:
在IT部门:
- Max的工资最高
- 兰迪和乔都赚取第二高的独特的薪水
- 威尔的薪水是第三高的
在销售部:
- 亨利的工资最高
- 山姆的薪水第二高
- 没有第三高的工资，因为只有两名员工

select
m.Department as “Department”,
m.Employee as “Employee”,
m.Salary as “Salary”
from
(
SELECT b.name AS “DEPARTMENT”,
a.name AS “EMPLOYEE”,
a.Salary,
DENSE_RANK() OVER(partition by a.departmentId ORDER BY a.salary desc) rank
FROM Employee a,Department b
where a.departmentId = b.id
) m where rank<=3；

select
m.Department,
m.Employee,
m.Salary
from (
SELECT b.name AS ‘Department’,
a.name AS ‘Employee’,
a.Salary,
DENSE_RANK() OVER w AS ‘rank’
FROM Employee a,Department b
where a.departmentId = b.id
WINDOW w AS (partition by a.departmentId ORDER BY a.salary desc)
) m where m.rank<=3;