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(DISTINCT s.challenge_id) > 1
ORDER BY    COUNT(DISTINCT s.challenge_id)  DESC , h.hacker_id ASC