select h.hacker_id, h.name, sum(scr) as fs from hackers as h join 
(select s.hacker_id, s.challenge_id, max(s.score) as scr from submissions as s
group by s.hacker_id, s.challenge_id having scr > 0) as t1   
on h.hacker_id = t1.hacker_id
group by h.hacker_id  
order by fs desc, h.hacker_id;