【SQL】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.

 SELECT DISTINCT Salary AS SecondHighestSalary
 FROM Employee
 UNION SELECT null
 ORDER BY SecondHighestSalary DESC
 LIMIT 1,1;