Please help!

why this code is not working ? I removed only the sub-queries and it is giving larger values. I don't understand why sub-queries is making any difference.

Changed code :

select con.contest_id,
        con.hacker_id, 
        con.name, 
        sum(total_submissions), 
        sum(total_accepted_submissions), 
        sum(total_views), sum(total_unique_views)
    from contests con 
    join colleges col on con.contest_id = col.contest_id 
    join challenges cha on  col.college_id = cha.college_id 

        left join view_stats vs 
        on cha.challenge_id = vs.challenge_id 
        left join submission_stats ss
        on cha.challenge_id = ss.challenge_id

    group by con.contest_id, con.hacker_id, con.name
    having sum(total_submissions)!=0 or 
    sum(total_accepted_submissions)!=0 or
    sum(total_views)!=0 or
    sum(total_unique_views)!=0
    order by contest_id;