SecondHighestSalary.sql

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


-- Solution:
-- Write your PostgreSQL query statement below
select max(ranked_employee.salary) SecondHighestSalary from 
(select salary,
    dense_rank() over (
        order by salary desc
    ) salary_rank
from Employee
) ranked_employee where ranked_employee.salary_rank = 2