mysql - Sort comments by upvotes-downvotes, make sure ones without votes are displayed above negative -

i'm fetching comments , sorting them score (upvotes-downvotes). if comment has not been voted on @ all, has null upvotes & downvotes, , ones negative displayed first.

upvotes cv_type = 1, downvotes cv_type = 0.

select c_id,c_text,c_date,c_parentid,u_username, (select sum(if( cv.cv_type=  '1', 1 ,  0 )) comment_votes cv cv_commentid=comments.c_id ) upvotes, (select sum(if( cv.cv_type=  '0', 1 ,  0 )) comment_votes cv cv_commentid=comments.c_id ) downvotes comments inner join users on u_id = c_userid c_postid = ? , c_parentid = 0 order upvotes-downvotes desc limit 100 

any way make sure ones without votes above ones negative?

just use coalesce() function replace null values 0:

select c_id, c_text, c_date, c_parentid, u_username,        coalesce((select sum(cv.cv_type = '1') comment_votes cv cv.cv_commentid= c.c_id ), 0) upvotes,        coalesce((select sum(cv.cv_type = '0') comment_votes cv cv.cv_commentid = c.c_id ), 0) downvotes comments c inner join      users u      on u.u_id = c.c_userid c.c_postid = ? , c.c_parentid = 0 order upvotes - downvotes desc limit 100; 

note: should use table aliases , qualified column names instead of naming columns in table prefix. instead of using c_parentid, use c.parentid. prefixes on column names useful, sql uses table aliases identify table column comes from.