180612_Nth_highest

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