从数据库中选择所有的喜欢和不喜欢

Question

如何选择数据库中有喜欢的所有职位。而且我还希望所有没有喜欢的帖子都列在同一个SQL查询中。喜欢被存储在一个表和每个表conncted到后与外键

SELECT likes.*, posts. * , profile . *, credentials.username, posts.session_sessionid as sSession 
FROM likes, posts, follows, profile, credentials 
WHERE follows.users = posts.userId 
AND profile.userId= follows.users 
AND profile.userId = credentials.profle_userId 
AND posts.session_sessionId IS NOT NULL 
AND likes.idposts = posts.idposts ORDER BY posts.date DESC` 

Answer 1

使用outer join代替。如果你想给like count添加到结果，一个选择是使用其它子查询，以获得count：

SELECT likes.*, t.likecount, posts.* ,profile.*, credentials.username, 
     posts.session_sessionid as sSession 
FROM posts 
    join follows on follows.users = posts.userId 
    join profile on profile.userId= follows.users 
    join credentials on profile.userId = credentials.profle_userId 
    left join likes on likes.idposts = posts.idposts 
    left join (
     select idposts, count(*) likecount 
     from likes 
     group by idposts 
    ) t on t.idposts = posts.idposts 
WHERE posts.session_sessionId IS NOT NULL 
ORDER BY posts.date DESC` 

一般来说，我不会推荐的from子句中使用逗号。