Leetcode177. Nth Highest Salary

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 |
+————————+

和上一題沒什麼差別，輸出第2個和第n個是一樣的。

CREATE FUNCTION getNthHighestSalary(N INT) RETURNS INT
BEGIN
DECLARE M INT;
SET M=N-1;

  RETURN (
      # Write your MySQL query statement below.
      SELECT IFNULL( 
    (SELECT DISTINCT Salary FROM Employee 
     ORDER BY Salary DESC LIMIT M,1) ,
    NULL)
  );
END