177. Nth Highest Salary

Description

Write a SQL query to get the n^th highest salary from the Employee table.

+----+--------+
| Id | Salary |
+----+--------+
| 1  | 100    |
| 2  | 200    |
| 3  | 300    |
+----+--------+

For example, given the above Employee table, the n^th highest salary where n = 2 is 200. If there is no n^th highest salary, then the query should return null.

+------------------------+
| getNthHighestSalary(2) |
+------------------------+
| 200                    |
+------------------------+

My Solution

Source Code

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CREATE FUNCTION getNthHighestSalary(@N INT) RETURNS INT AS
BEGIN
    RETURN (
        SELECT DISTINCT Salary
        FROM Employee
        ORDER BY Salary DESC
        OFFSET @N - 1 ROWS
        FETCH NEXT 1 ROWS ONLY
    );
END

Analysis

This one is basically the same as the 2nd Highest Salary problem, only this time instead of using a hardcoded value for the offset, we have a variable now. We get the unique salaries and sort them so they're in order. Then we select the one at offset N-1 since OFFSET is from the first row.