select
    a.hacker_id
    , d.name
from submissions a
join challenges b
    on a.challenge_id = b.challenge_id
join difficulty c
    on b.difficulty_level = c.difficulty_level
    and a.score = c.score
left join hackers d
    on a.hacker_id = d.hacker_id
where a.score = c.score
group by 1,2
having count(distinct a.challenge_id) > 1
order by count(distinct a.challenge_id) desc,a.hacker_id