with ect1 as (SELECT Co.contest_id, Co.hacker_id, Co.name, 
    sum(ss.total_submissions) as 's1', 
    sum(ss.total_accepted_submissions) as 's2'
    FROM Contests co
    JOIN Colleges col ON Co.contest_id  = Col.contest_id 
    JOIN Challenges ch ON Col.college_id = Ch.college_id
    JOIN Submission_Stats ss ON Ch.challenge_id = Ss.challenge_id
    GROUP BY Co.contest_id, Co.hacker_id, Co.name),

ect2 as (SELECT Co.contest_id, Co.hacker_id, Co.name, 
    sum(vs.total_views) as 's3', 
    sum(vs.total_unique_views) as 's4'
    FROM Contests co
    JOIN Colleges col ON Co.contest_id  = Col.contest_id 
    JOIN Challenges ch ON Col.college_id = Ch.college_id
    JOIN View_Stats vs ON Ch.challenge_id = vs.challenge_id
    GROUP BY Co.contest_id, Co.hacker_id, Co.name)

SELECT ect1.contest_id, ect1.hacker_id, ect1.name, 
    ect1.s1, ect1.s2, ect2.s3, ect2.s4
FROM ect1 FULL JOIN ect2 ON ect1.contest_id = ect2.contest_id and ect1.hacker_id = ect2.hacker_id and ect1.name = ect2.name
WHERE  ect1.s1+ ect1.s2+ ect2.s3+ ect2.s4 <>0
ORDER BY ect1.contest_id