LeetCode 177. Nth Highest Salary （mysql limit 和 offset用法）

Description:

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 |
±-----------------------+

Solution:

首先申明 M = N - 1
limit M，N 表示從第M條結果開始往後讀N條記錄
也可以寫成 limit 1 offset M 表示從M條後讀一條數據

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
      //limit 1 offset M  也是可以的
  );
END