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SELECT con.contest_id, con.hacker_id, con.name, 
SUM(sg.total_submissions), SUM(sg.total_accepted_submissions), 
SUM(vg.total_views), SUM(vg.total_unique_views)
FROM Contests AS con
JOIN Colleges AS col ON con.contest_id = col.contest_id
JOIN Challenges AS cha ON cha.college_id = col.college_id
LEFT JOIN
(SELECT ss.challenge_id, SUM(ss.total_submissions) AS total_submissions, SUM(ss.total_accepted_submissions) AS total_accepted_submissions FROM Submission_Stats AS ss GROUP BY ss.challenge_id) AS sg
ON cha.challenge_id = sg.challenge_id
LEFT JOIN
(SELECT vs.challenge_id, SUM(vs.total_views) AS total_views, SUM(vs.total_unique_views) AS total_unique_views
FROM View_Stats AS vs GROUP BY vs.challenge_id) AS vg
ON cha.challenge_id = vg.challenge_id
GROUP BY con.contest_id, con.hacker_id, con.name
HAVING SUM(sg.total_submissions) +
       SUM(sg.total_accepted_submissions) +
       SUM(vg.total_views) +
       SUM(vg.total_unique_views) > 0
ORDER BY con.contest_id;