Question

I don’t know where else to ask. I have this query:

SELECT po.* FROM posts po, follows f, user pn
                  WHERE (f.follower_id = #{id}
                    AND f.followed_id = pn.id
                    AND po.user_id = pn.id)
                    OR (po.user_id = #{id})
                  ORDER BY created_at DESC LIMIT 10 OFFSET #{offset}

I get the posts from the followers correctly, but not the posts by the user himself. It seems as if the second part of the OR is always ignored.

SELECT * FROM posts WHERE user_id = #{id}

works fine, though.

EDIT

I am sorry, I accidentally hit enter before I was done with the text!!

EDIT 2

This now seems to work:

SELECT DISTINCT po.* FROM users pn
                    INNER JOIN follows f ON f.follower_id = #{id}
                    INNER JOIN posts po ON po.user_id = f.followed_id OR po.user_id = #{id}
                  ORDER BY created_at DESC LIMIT 10 OFFSET #{offset}

Maybe someone can tell me why?

Answer 1

Try this:

SELECT po.* FROM posts po, follows f, user pn
  WHERE f.follower_id = #{id}
    AND f.followed_id = pn.id
    AND (   po.user_id = pn.id
         OR po.user_id = #{id})
  ORDER BY created_at DESC LIMIT 10 OFFSET #{offset}

The implicit joins were not being considered in the second case. This is one of the reasons I shy away from implicit joins, instead using explicit INNER JOIN clauses.

If this doesn’t get the results you are looking for, you might need to consider a UNION instead. Your description is a bit vague and you have not given us your schema, so I can’t tell if this query will work or not.