select 
c.contest_id, 
c.hacker_id, 
c.name, 
sum(ss.total_submissions), 
sum(ss.total_accepted_submissions),
sum(vs.total_views),
sum(vs.total_unique_views)
from Contests c
INNER JOIN Colleges co ON c.contest_id = co.contest_id
INNER JOIN Challenges ch ON co.college_id = ch.college_id
INNER JOIN View_Stats vs ON ch.challenge_id = vs.challenge_id
INNER JOIN Submission_Stats ss ON vs.challenge_id = ss.challenge_id
group by c.contest_id,c.hacker_id,c.name
having sum(ss.total_submissions)+sum(ss.total_accepted_submissions)+ sum(vs.total_views)+sum(vs.total_unique_views)>0 
order by c.contest_id;