sql - MySQL sum negative and sum of positive values without sub query -

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sql - MySQL sum negative and sum of positive values without sub query -

i have 2 tables follows:

tbl_answers : id, (fk)authorid ... tbl_answer_votes : id, (fk)voterid, (fk)answerid, vote (sint, ever -1 or 1)

tbl_answers has 1 many relationship tbl_answer_votes , vote can either negative 1 or positive 1.

i need bring together tbl_answer_votes on tbl_answers produce sum of negative votes reply , sum of positive votes reply 2 separate columns.

i can sub-querying little part of larger query , after reading pitfalls on sub-queries seek , produce 2 negative , positive sums votes table efficiently possible.

you can utilize case , join accomplish this:

select a.id, sum(case v.vote when 1 1 else 0 end) upvotes, sum(case v.vote when -1 1 else 0 end) downvotes tbl_answers inner bring together tbl_answer_votes v on v.id = a.id grouping a.id

this returns id tbl_answers , 2 columns total votes of either value tbl_answer_votes. didn't specify (if any) other columns you'd want either table, may have adjust column list in select , group by portions add together additional columns.

mysql sql

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