Leetcode 177. Nth Highest Salary数据库

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

题目链接：https://leetcode.com/problems/nth-highest-salary/

方法一：

CREATE FUNCTION getNthHighestSalary(N INT) RETURNS INT
BEGIN
    set N = N-1;
  RETURN (
      # Write your MySQL query statement below.
      select distinct Salary from Employee order by Salary desc limit N,1
  );
END

方法二：

CREATE FUNCTION getNthHighestSalary(N INT) RETURNS INT
BEGIN
  declare m int;
  set m = n - 1;
  RETURN (
      # Write your MySQL query statement below.
      select distinct Salary from Employee order by Salary desc limit m, 1
  );
END

方法三：

CREATE FUNCTION getNthHighestSalary(N INT) RETURNS INT
BEGIN
declare m int;
  set m = n - 1;
  RETURN (
      # Write your MySQL query statement below.
      
select coalesce((select distinct salary from employee order by salary desc limit m,1)) as SecondHighestSalary
  );
END