with pr as
(
    select h.name, s.hacker_id, s.challenge_id, s.score,
    ROW_NUMBER() over (partition by h.hacker_id, s.challenge_id order by score desc) as crnk
    from hackers h join submissions s on h.hacker_id = s.hacker_id
),
dr as 
(
    select name, hacker_id, SUM(score) as scr
    from pr
    where crnk = 1
    group by name, hacker_id
)

select hacker_id, name, scr
from dr 
where scr <> 0
order by scr desc, hacker_id asc