Sie haben es mit Ihrer Anfrage fast geschafft. Verwenden Sie einfach filter -Klausel, um die Stimmenzahl des aktuellen Benutzers abzurufen
SELECT
post.postID as postID,
post.title as title,
post.author as author,
post.created as created,
COALESCE(sum(votes.vote), 0) as voteCount,
COALESCE(sum(votes.vote) filter (where votes.username= 'username'), 0) as userVote -- in '' just provide username for current login user
FROM post
LEFT JOIN votes ON post.postID = votes.postID
GROUP BY 1,2,3,4
ORDER BY 5 DESC
Eine andere Möglichkeit besteht darin, eine weitere linke Verknüpfung wie unten zu verwenden:
SELECT
p.postID as postID,
p.title as title,
p.author as author,
p.created as created,
COALESCE(sum(v1.vote), 0) as voteCount,
COALESCE(v2.vote , 0) as userVote -- in '' just provide username for current login user
FROM post p
LEFT JOIN votes v1 ON p.postID = v1.postID
LEFT JOIN votes v2 on p.postID = v2.postID and v2.username='username'
GROUP BY 1,2,3,4,v2.vote
ORDER BY 5 DESC
