Question

Database Scheme:
http://pastebin.com/aPXk1rMf

I’m want to select “post owner’s uName” and “comment owner’s uName” from “comments” table (i.e. I think I need cOwnerID>uName and pID>uID>uName) so that I can log some activities right after a comment is posted.
I tried to use MySQL joins in order to achieve that but I couldn’t; so here’s what I tried in vain.

$result = dbquery("INSERT INTO comments VALUES ('','$pID','$ownerID','$cmnt')"); // inserting a comment

$lastID = mysql_insert_id();

$res = dbquery("SELECT
                users.username AS username
            FROM `comments`
            LEFT JOIN `users` on comments.cOwnerID = users.uID
            WHERE (cID='$lastID')");

Answer 1

I think you have to use aliases for table users, because, actually, you will have two joins on this table : one for the post author and another for the comment’s author.

Try something like this :

            SELECT
                commentAuthor.username AS commentauthor_username,
                postAuthor.username AS postauthor_username
            FROM `comments`
            LEFT JOIN `users` AS commentAuthor on comments.cOwnerID = commentAuthor.uID
            LEFT JOIN `posts` on posts.pId = comments.pID
            LEFT JOIN `users` AS postAuthor on posts.uID = postAuthor.uID
            WHERE (cID='$lastID')