LeetCode SQL: Second Highest Salary

select if(count(salary) = 0, NULL, salary) as `salary` from (

select salary from Employee  group by salary order by salary desc limit 1,1) tmp

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.

对于null的处理稍烦