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LeetCode

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Problem

The Employee table holds all employees. Every employee has an Id, a salary, and there is also a column for the department Id.

+----+-------+--------+--------------+
| Id | Name  | Salary | DepartmentId |
+----+-------+--------+--------------+
| 1  | Joe   | 70000  | 1            |
| 2  | Jim   | 90000  | 1            |
| 3  | Henry | 80000  | 2            |
| 4  | Sam   | 60000  | 2            |
| 5  | Max   | 90000  | 1            |
+----+-------+--------+--------------+

The Department table holds all departments of the company.

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

Write a SQL query to find employees who have the highest salary in each of the departments. For the above tables, your SQL query should return the following rows (order of rows does not matter).

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

Explanation:

Max and Jim both have the highest salary in the IT department and Henry has the highest salary in the Sales department.

Code

出现相同的最大工资，需要都保留，max 只会返回一个值

SELECT
    Department.name AS Department,
    Employee.name AS Employee,
    Salary
FROM
    Employee
    JOIN Department
    ON Employee.DepartmentId = Department.Id
WHERE
(Employee.DepartmentId , Salary) IN
(
    SELECT DepartmentId, MAX(Salary)
    FROM Employee
    GROUP BY DepartmentId
)