# 0176. Second Highest Salary

<https://leetcode.com/problems/second-highest-salary>

## Description

Table: `Employee`

```
+-------------+------+
| Column Name | Type |
+-------------+------+
| Id          | int  |
| Salary      | int  |
+-------------+------+
Id is the primary key column for this table.
Each row of this table contains information about the salary of an employee.
```

Write an SQL query to report the second highest salary from the `Employee` table. If there is no second highest salary, the query should report `null`.

The query result format is in the following example.

**Example 1:**

```
**Input:** 
Employee table:
+----+--------+
| Id | Salary |
+----+--------+
| 1  | 100    |
| 2  | 200    |
| 3  | 300    |
+----+--------+
**Output:** 
+---------------------+
| SecondHighestSalary |
+---------------------+
| 200                 |
+---------------------+
```

**Example 2:**

```
**Input:** 
Employee table:
+----+--------+
| Id | Salary |
+----+--------+
| 1  | 100    |
+----+--------+
**Output:** 
+---------------------+
| SecondHighestSalary |
+---------------------+
| Null                |
+---------------------+
```

## ac

```java
```
