[hackerrank] MySQL - Contest Leaderboard

select h.hacker_id, h.name, sum(b.score) as sum_score
from hackers as h
join (select hacker_id, challenge_id, max(score) as score
from submissions
group by hacker_id, challenge_id
      ) as b on h.hacker_id = b.hacker_id
group by 1,2
having sum_score > 0
order by sum_score desc, hacker_id asc