Hi!

This seems to be working. which I basically used a lot of your code to write my code but I dont think I really know whats happening. In particular when I remove the 'group by' command I expect to get a lot more records (since we are not grouping anymore) but I get only one record and I dont understand why. Can you please explain whats happening here? thanks

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