Leetcode 184 Employees with the highest wages in the Department (July 3, 2022)

Create table If Not Exists Employee (id int, name varchar(255), salary int, departmentId int)
Create table If Not Exists Department (id int, name varchar(255))
Truncate table Employee
insert into Employee (id, name, salary, departmentId) values ('1', 'Joe', '70000', '1')
insert into Employee (id, name, salary, departmentId) values ('2', 'Jim', '90000', '1')
insert into Employee (id, name, salary, departmentId) values ('3', 'Henry', '80000', '2')
insert into Employee (id, name, salary, departmentId) values ('4', 'Sam', '60000', '2')
insert into Employee (id, name, salary, departmentId) values ('5', 'Max', '90000', '1')
Truncate table Department
insert into Department (id, name) values ('1', 'IT')
insert into Department (id, name) values ('2', 'Sales')

surface ： Employee

±-------------±--------+
| Name | type |
±-------------±--------+
| id | int |
| name | varchar |
| salary | int |
| departmentId | int |
±-------------±--------+
id Is the primary key column of this table .
departmentId yes Department In the table ID The foreign key .
Each row of this table represents the employee's ID、 Name and salary . It also includes their department's ID.

surface ： Department

±------------±--------+
| Name | type |
±------------±--------+
| id | int |
| name | varchar |
±------------±--------+
id Is the primary key column of this table .
Each row of this table represents the of a department ID And its name .

To write SQL Query to find the highest paid employee in each department .
Press In any order Return result table .
The query result format is shown in the following example .

Example 1:

Input ：
Employee surface :
±—±------±-------±-------------+
| id | name | salary | departmentId |
±—±------±-------±-------------+
| 1 | Joe | 70000 | 1 |
| 2 | Jim | 90000 | 1 |
| 3 | Henry | 80000 | 2 |
| 4 | Sam | 60000 | 2 |
| 5 | Max | 90000 | 1 |
±—±------±-------±-------------+
Department surface :
±—±------+
| id | name |
±—±------+
| 1 | IT |
| 2 | Sales |
±—±------+
Output ：
±-----------±---------±-------+
| Department | Employee | Salary |
±-----------±---------±-------+
| IT | Jim | 90000 |
| Sales | Henry | 80000 |
| IT | Max | 90000 |
±-----------±---------±-------+
explain ：Max and Jim stay IT The wages of all departments are the highest ,Henry The highest salary is in the sales department .

source ： Power button （LeetCode）
link ：https://leetcode.cn/problems/department-highest-salary

Method 1 ：JOIN and IN sentence

MySQL Submission ：

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
	)
;