MySQL code

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

Guys,

I messed it up because I didn't carefully read the table description. challenges.hacker_id is the id of the hacker that CREATED the challenge, not the id of the guy that participated in it.

Take care of that, because this join condition ruins everything ;)

I'M YELLING BECAUSE IT IS RIDICULOUS THAT A SCORE GREATER THAN A FULL SCORE IS NOT A "FULL SCORE"

It's like getting extra credit is crap, it's like the losing team in soccer getting more goals. It's like.... WTF man.

Upvote this to support your fellow hackers and spread the word!

My Solution)

Most simple sql

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

SQL Solution, hope it helps. The main thing is using having

/* join tables together, to make a master table which contains all the info */ select sub.hacker_id, hak.name from submissions sub join challenges cha on sub.challenge_id = cha.challenge_id join hackers hak on sub.hacker_id = hak.hacker_id join difficulty dif on cha.difficulty_level = dif.difficulty_level

/* filter logic, to eliminate submissions that did not earn full score */ where dif.score = sub.score

/* further eliminate hackers who only had one full-score submission */ group by sub.hacker_id, hak.name having count(sub.score) > 1

/* display by the order stated in the proble, */ order by count(sub.score) desc, sub.hacker_id