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LeetCode 184. 部門工資最高的員工

Employee 表包含所有員工資訊,每個員工有其對應的 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 表包含公司所有部門的資訊。

+----+----------+
| Id | Name     |
+----+----------+
| 1  | IT       |
| 2  | Sales    |
+----+----------+

編寫一個 SQL 查詢,找出每個部門工資最高的員工。例如,根據上述給定的表格,Max 在 IT 部門有最高工資,Henry 在 Sales 部門有最高工資。

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

思路1:通過連表,判斷相應的最高工資

select d.name as Department,e.name as Employee,e.Salary
from Department as d,Employee as e
where d.Id=e.DepartmentId and e.Salary=(Select max(Salary) from Employee where DepartmentId=d.Id)

思路2:通過group by 把每個部門的最高工資查出來,再通過連表

SELECT
d.`Name` AS Department ,
e.`Name` AS Employee ,
e.Salary
FROM (SELECT departmentId,max(Salary) AS Salary FROM employee GROUP BY DepartmentId) AS x,
employee AS e,department AS d
WHERE x.departmentId=e.DepartmentId and x.Salary=e.Salary and e.DepartmentId=d.Id