176_Second_Highest_Salary.sql

-- Source: https://leetcode.com/problems/second-highest-salary/description/?envType=study-plan-v2&envId=top-sql-50

-- Table: Employee

-- +-------------+------+
-- | Column Name | Type |
-- +-------------+------+
-- | id          | int  |
-- | salary      | int  |
-- +-------------+------+
-- id is the primary key (column with unique values) for this table.
-- Each row of this table contains information about the salary of an employee.

-- Write a solution to find the second highest salary from the Employee table. If there is no second highest salary, return null (return None in Pandas).

-- The 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                |
-- +---------------------+

------------------------------------------------------------------------------

-- SQL Schema

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')

-- MS SQL Server Code

SELECT (
    SELECT DISTINCT salary
     FROM Employee
     ORDER BY salary DESC
     OFFSET 1 ROW
     FETCH NEXT 1 ROW ONLY
) AS SecondHighestSalary;