LeetCode 177. Nth Highest Salary

https://leetcode.com/problems/nth-highest-salary/description/

Write a SQL query to get the nth highest salary from the Employee table.

+----+--------+
| Id | Salary |
+----+--------+
| 1  | 100    |
| 2  | 200    |
| 3  | 300    |
+----+--------+

For example, given the above Employee table, the nth highest salary where n = 2 is 200. If there is no nth highest salary, then the query should return null.

+------------------------+
| getNthHighestSalary(2) |
+------------------------+
| 200                    |
+------------------------+

---

Create table If Not Exists Employee (Id int, Salary int);
Truncate table Employee;
insert into Employee (Id, Salary) values ('1', '100');
insert into Employee (Id, Salary) values ('2', '200');
insert into Employee (Id, Salary) values ('3', '300');

CREATE FUNCTION getNthHighestSalary(N INT) RETURNS INT
BEGIN
DECLARE M INT;
SET M = N - 1;
  RETURN (
      # Write your MySQL query statement below.
      SELECT
        (SELECT Salary
        FROM Employee
        ORDER BY Salary DESC
        LIMIT M, 1) AS getNthHighestSalary      
  );
END