组合两个表#175

Create table If Not Exists Employee (Id int, Salary int)
Truncate table Employee
insert into Employee (Id, Salary) values ('1', '100')
insert into Employee (Id, Salary) values ('2', '200')
insert into Employee (Id, Salary) values ('3', '300')

+----+--------+
| Id | Salary |
+----+--------+
| 1  | 100    |
| 2  | 200    |
| 3  | 300    |
+----+--------+ 例如上述 `Employee` 表，`SQL`查询应该返回 `200 `作为第二高的薪水。如果不存在第二高的薪水，那么查询应返回 `null`。

+---------------------+
| SecondHighestSalary |
+---------------------+
| 200                 |
+---------------------+

# Write your MySQL query statement below
select (select distinct Salary from Employee order by Salary desc limit 1 offset 1) as SecondHighestSalary;

{"headers": {"Employee": ["Id", "Salary"]}, "rows": {"Employee": [[1, 100], [2, 200], [3, 300]]}}

{"headers":["SecondHighestSalary"],"values":[[200]]}