177. Nth Highest Salary

Giới thiệu bài toán

Chi tiết: https://leetcode.com/problems/nth-highest-salary/

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.

Yêu cầu

Write a solution to find the nth highest salary from the Employee table. If there is no nth highest salary, return null.

The 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

Giải quyết bài toán

CREATE FUNCTION getNthHighestSalary(N INT) RETURNS INT
BEGIN
    DECLARE offset INT;
    SET offset = N - 1;
    RETURN (
        SELECT DISTINCT(salary)
        FROM Employee
        ORDER BY salary DESC
        LIMIT 1 OFFSET offset
    );
END

Tham khảo: https://leetcode.com/submissions/detail/1038477455/