Leetcode176. Second Highest Salary

Write a SQL query to get the second highest salary from the Employee table.

+—-+——–+

| Id | Salary |

+—-+——–+

| 1 | 100 |

| 2 | 200 |

| 3 | 300 |

+—-+——–+

For example, given the above Employee table, the query should return 200 as the second highest salary. If there is no second highest salary, then the query should return null.

+———————+

| SecondHighestSalary |

+———————+

| 200 |

+———————+

找出第二大的数字，这道题遇到的两个坑是，没有第二大的时候需要返回的是null，第二个使用select ifnull（）后忘记加别名，开始加到了里面，显然是错的。

SELECT IFNULL(
(SELECT DISTINCT Salary FROM Employee
ORDER BY Salary DESC LIMIT 1 OFFSET 1) ,
NULL) AS SecondHighestSalary;