sql - Difference of 2 columns of query -

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i have votequestion table: votequestion(iduser → user, idquestion → content, isup)

and question table: question(idquestion → content, title)

i want select 5 questions best score (upvotes-downvotes).
upvote votequestion isup = true , downvote votequestion isup = false.

i tried following query, it's not looking for. it's giving same score every question.

with upvotes (    select count(*) "a"   "votequestion", "question"   "votequestion"."idquestion" = "question"."idquestion"   , "votequestion"."isup" true ),  downvotes (    select count(*) "b"   "votequestion", "question"   "votequestion"."idquestion" = "question"."idquestion"   , "votequestion"."isup" false ) select "title", "question"."idquestion", upvotes."a"-downvotes."b" total "votequestion", "question", upvotes, downvotes "votequestion"."idquestion" = "question"."idquestion" group "title", "question"."idquestion", upvotes."a", downvotes."b" order "total" desc limit 5

also tried this:

select "title", "question"."idquestion",  ( select count(*)    "votequestion", "question"   "votequestion"."idquestion" = "question"."idquestion"   , "votequestion"."isup" true ) upvotes,  ( select count(*)    "votequestion", "question"   "votequestion"."idquestion" = "question"."idquestion"   , "votequestion"."isup" false ) downvotes, upvotes-downvotes total "votequestion", "question" "votequestion"."idquestion" = "question"."idquestion" group "title", "question"."idquestion" order total desc limit 5

but says error: column "upvotes" not exist

how can difference of upvotes , downvotes in column query?

with conditional statement inline convert true , false values numbers (1 , -1 respectively) can sum votes this:

select     q."title",     q."idquestion",     sum(        case            when v."isup" 1            else -1        end     ) total      votequestion v join question q on v."idquestion" = q."idquestion"  group     q."title",     q."idquestion"  order     3 desc  limit 5

i haven't tried yet i'm pretty sure works.

edit: here's sqlfiddle runs successfully: http://sqlfiddle.com/#!15/df4ca/3


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