leetcode 176. 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 second highest salary is 200. If there is no second highest salary, then the query should return null.

找到表中第二大的值

注意查询出来的列名为"SecondHighestSalary",如果没有第二大的值返回null

select IFNULL ((select Salary from Employeegroup by Salaryorder by Salary DESClimit 1,1),null) as SecondHighestSalary