Unable to identify syntax issue with using MAX and OVER PARTITION BY - mysql

Question

I'm trying to answer a SQL Leetcode question on Medium Difficulty. The question is asking me to find the people that have the highest salary per department.
I tried using GROUP BY but wasn't able to figure out that approach so I tried to use the PARTITION BY in order to find the max salary for each department. Afterwards, I would add a final WHERE statement where I could filter down to people with a salary that equals the max salary.
This is the query I have so far:
SELECT
Department.Name AS Department,
Employee.Name AS Employee,
Employee.Salary,
MAX(Employee.Salary) OVER (PARTITION BY Department.Name) AS MaxSalary
FROM Employee
LEFT JOIN Department ON Department.id = Employee.DepartmentId
;
There's two tables.
EMPLOYEE TABLE:
+----+-------+--------+--------------+
| 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 TABLE:
+----+----------+
| Id | Name |
+----+----------+
| 1 | IT |
| 2 | Sales |
+----+----------+
and the correct output should look like this.
CORRECT EXPECTED OUTPUT:
+------------+----------+--------+
| Department | Employee | Salary |
+------------+----------+--------+
| IT | Max | 90000 |
| IT | Jim | 90000 |
| Sales | Henry | 80000 |
+------------+----------+--------+
Running my current query leads to a runtime error with this message:
You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '(PARTITION BY Department.Name) AS MaxSalary
FROM Employee
LEFT JOIN Department O' at line 7
I've looked over the syntax multiple times so I assume it's a incorrect understanding of how PARTITION BY works. I was expecting that I would see the max salary for each department listed on the right for each individual. Something like this:
+----+-------+--------+--------------+-----------+
| Id | Name | Salary | DepartmentId | MaxSalary |
+----+-------+--------+--------------+-----------+
| 1 | Joe | 70000 | 1 | 90000 |
| 2 | Jim | 90000 | 1 | 90000 |
| 3 | Henry | 80000 | 2 | 80000 |
| 4 | Sam | 60000 | 2 | 80000 |
| 5 | Max | 90000 | 1 | 90000 |
+----+-------+--------+--------------+ -----------+
After achieving that, I was going to add this line:
WHERE Employee.Salary = MaxSalary;
What is the proper way to do this?

Answer 1

You can consider using one of the following:
SELECT D.Name AS Department, E.Name AS Employee, E.Salary
FROM Employee AS E LEFT JOIN Department AS D ON E.DepartmentId = D.id
WHERE (E.Salary = (SELECT MAX(X.Salary) FROM Employee AS X WHERE (X.DepartmentId = E.DepartmentId)));
SELECT D.Name AS Department, E.Name AS Employee, E.Salary
FROM Employee AS E LEFT JOIN Department AS D ON E.DepartmentId = D.id
INNER JOIN (SELECT DepartmentId, MAX(Salary) AS MaxSalary FROM Employee GROUP BY DepartmentId) AS X ON E.DepartmentId = X.DepartmentId AND E.Salary = X.MaxSalary;