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