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                    |
+------------------------+

此题与上一题大同小异。代码如下：

CREATE FUNCTION getNthHighestSalary(N INT) RETURNS INT
BEGIN
  DECLARE M INT;
  SET M=N-1;
  RETURN (
      # Write your MySQL query statement below.
      Select
        (Select Distinct Salary
        From Employee
        Order By Salary Desc
        Limit 1 Offset M) AS N_th_HighestSalary
  );
END