문제 link
https://www.hackerrank.com/challenges/placements/problem
Code link
https://github.com/JamesJung01/Hackerrank_sql/blob/main/02_Medium/Placements.sql
SELECT s.Name FROM students AS s JOIN friends AS f ON s.id = f.id JOIN packages AS p1 ON f.id = p1.id JOIN packages AS p2 ON f.friend_id = p2.id WHERE p1.salary < p2.salary ORDER BY p2.salary;