[176_MEDIUM] Second Highest Salary

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                |
+---------------------+

 

문제 조건 

두 번째로 높은 급여를 출력하시오

두 번째로 높은 급여가 없는 경우 null을 출력하시오 

 

문제 풀이

# limit 1 offset 1 (limit 1,1로 표현 가능) 

select ifnull((select distinct salary
			   from employee
               order by salary desc
               limit 1 offset 1),null) as SecondHighestSalary