Question 4

SELECT H.hacker_id, H.name 
FROM Submissions as S join Hackers as H 
on s.hacker_id = h.hacker_id 
join Challenges as C on S.challenge_id = C.challenge_id
join Difficulty as D on C.Difficulty_level = D.Difficulty_level
WHERE S.score = D.score 
GROUP BY H.hacker_id, H.name 
HAVING count(s.submission_id) > 1
ORDER BY count(s.submission_id) DESC, H.hacker_id ASC;