Leetcode 177 The nth highest salary (June 26, 2022)

SQL framework ：

Create table If Not Exists Employee (Id int, Salary int)
Truncate table Employee
insert into Employee (id, salary) values ('1', '100')
insert into Employee (id, salary) values ('2', '200')
insert into Employee (id, salary) values ('3', '300')

±------------±-----+
| Column Name | Type |
±------------±-----+
| id | int |
| salary | int |
±------------±-----+
Id Is the primary key column of the table .
Each row of the table contains information about the employee's salary .

Write a SQL Query to report Employee No n High wages . If there is no n A maximum wage , The query should be reported as null .

The query result format is as follows .

Example 1:

Input :
Employee table:
±—±-------+
| id | salary |
±—±-------+
| 1 | 100 |
| 2 | 200 |
| 3 | 300 |
±—±-------+
n = 2
Output :
±-----------------------+
| getNthHighestSalary(2) |
±-----------------------+
| 200 |
±-----------------------+
Example 2:

Input :
Employee surface :
±—±-------+
| id | salary |
±—±-------+
| 1 | 100 |
±—±-------+
n = 2
Output :
±-----------------------+
| getNthHighestSalary(2) |
±-----------------------+
| null |
±-----------------------+

source ： Power button （LeetCode）
link ：https://leetcode.cn/problems/nth-highest-salary

Method 1 ： The cartesian product

MySQL Submission ：

CREATE FUNCTION getNthHighestSalary(N INT) RETURNS INT
BEGIN
  RETURN (
      # Write your MySQL query statement below.
      SELECT 
          e1.salary
      FROM 
          employee e1, employee e2 
      WHERE 
          e1.salary <= e2.salary
      GROUP BY 
          e1.salary
      HAVING 
          count(DISTINCT e2.salary) = N
  );
END