select h.hacker_id, h.name
from difficulty as d
    join challenges as c on c.difficulty_level=d.difficulty_level
    join submissions as s on s.challenge_id=c.challenge_id
    join hackers as h on s.hacker_id=h.hacker_id
where s.score=d.score
group by 1,2
having count(s.score)>1
order by count(s.score) desc, 1;