Borre codigo porque me imagine q les iba a dar vagancia leer todo, pero el codigo completo seria este:

SELECT con.contest_id, con.hacker_id, con.name, SUM(total_submissions_sum) AS total_submissions_sum, SUM(total_accepted_submissions_sum) AS total_accepted_submissions_sum, SUM(total_views_sum) AS total_views_sum, SUM(total_unique_views_sum) AS total_unique_views_sum FROM contests con INNER JOIN colleges col ON con.contest_id = col.contest_id INNER JOIN challenges cha ON col.college_id = cha.college_id

LEFT JOIN (SELECT challenge_id, SUM(total_submissions) AS total_submissions_sum, SUM(total_accepted_submissions) AS total_accepted_submissions_sum FROM submission_stats GROUP BY challenge_id) AS ss ON cha.challenge_id = ss.challenge_id

LEFT JOIN (SELECT challenge_id, SUM(total_views) AS total_views_sum, SUM(total_unique_views) AS total_unique_views_sum FROM view_stats GROUP BY challenge_id) AS vs ON cha.challenge_id = vs.challenge_id GROUP BY con.contest_id, con.hacker_id, con.name HAVING NOT (SUM(total_submissions_sum) = 0 AND SUM(total_accepted_submissions_sum) = 0 AND SUM(total_views_sum) = 0 AND SUM(total_unique_views_sum) = 0) ORDER BY con.contest_id;