NthHighest_Salary.sql

/* -- 177. Nth Highest Salary..
SQL Schema
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 nth highest salary from the Employee table. If there is no nth 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    |
+----+--------+
n = 2
Output: 
+------------------------+
| getNthHighestSalary(2) |
+------------------------+
| 200                    |
+------------------------+
Example 2:

Input: 
Employee table:
+----+--------+
| id | salary |
+----+--------+
| 1  | 100    |
+----+--------+
n = 2
Output: 
+------------------------+
| getNthHighestSalary(2) |
+------------------------+
| null                   |
+------------------------+
 */

CREATE FUNCTION getNthHighestSalary(N INT) RETURNS INT
BEGIN

  RETURN (
      SELECT
        DISTINCT salary
        FROM
        (
			SELECT salary,
				DENSE_RANK() OVER(ORDER BY salary DESC) sal_rank
            FROM Employee
        )Temp
      WHERE sal_rank =N      
  );
END