leetcode-database-177. 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 .

题意：查询第n高的记录，如果没有请返回null

思路：按照salary排正序，使用limit挑选出第N高

最终sql：

CREATE FUNCTION getNthHighestSalary(N INT) RETURNS INT

BEGIN

declare M INT;

set M=N-1;

  RETURN (

      select DISTINCT SALARY from Employee order by SALARY DESC LIMIT M,1

  );

END