Use multiple mysql joins - mysql

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')

Answer 2

SELECT users1.username, users2.username FROM Posts p
WHERE p.pID="$POST_OF_INTEREST"
LEFT JOIN users users1 ON users1.uID=p.uID
LEFT OUTER JOIN comments ON comments.pID=p.pID
LEFT OUTER JOIN users users2 ON users2.uID=comments.cOwnerID
Given a particular post ID, this will get the username of the person who posted and the username of each person who commented on that post (one row per comment).

Answer 3

SELECT Users.uName AS UserNamePost
, UserComment.uName AS UserNameComment
FROM Users
INNER JOIN Posts
ON Posts.uID = Users.uID;
INNER JOIN Comments
ON Comments.pID = Posts.pID ;
INNER JOIN Users AS UserComment
ON Comments.cOwnerID = UserComment.uID ;
This will aim to have the user that has posted the post and then join the user for all comments for the post

Answer 4

"SELECT
users.username AS username,
comments.cOwnerID AS commentOwner,
users.uID AS userID
FROM
comments
LEFT JOIN
users
ON
commentOwner = userID
WHERE
commentOwner = '{$lastID}'";