MySql-三个成功连接的表，但未获得一列结果？

Question

I have three tables (user, post, comments) joined up (for an ajax powered social network thing I am doing for a degree).

So far so good but when I loop through them I am getting all the results except one. The reference to who commented on a post (stored within comments table) is coming up only as a number id (which should be joined to the user table but my join is obviously not working correctly!).

Any help very much appreciated! Probably something simple as I am still new at this PHP/mysql game!

MySQL tables:

           CREATE TABLE `post` (
           `pid` int(10) NOT NULL AUTO_INCREMENT,
           `uid` int(10) NOT NULL,
           `post` text NOT NULL,
           `pid_imageurl` varchar(100) NOT NULL,
           `likes` int(10) NOT NULL,
            PRIMARY KEY (`pid`)
            ) ENGINE=MyISAM  DEFAULT CHARSET=latin1 AUTO_INCREMENT=5 



           CREATE TABLE `user` (
           `uid` int(10) NOT NULL AUTO_INCREMENT,
           `name` varchar(20) NOT NULL,
           `password` varchar(20) NOT NULL,
           `uid_imageurl` varchar(100) NOT NULL,
           `joindate` varchar(11) NOT NULL,
           PRIMARY KEY (`uid`)
           ) ENGINE=MyISAM  DEFAULT CHARSET=latin1 AUTO_INCREMENT=9 ;


           CREATE TABLE `comments` (
           `cid` int(10) NOT NULL AUTO_INCREMENT,
           `comment_pid` int(10) NOT NULL,
           `comment_uid` int(10) NOT NULL,
           `comment` text NOT NULL,
            PRIMARY KEY (`cid`)
            ) ENGINE=MyISAM  DEFAULT CHARSET=latin1 AUTO_INCREMENT=4 ;

Code:

        $sql = "SELECT post.post, post.pid_imageurl, post.likes, user.name, comments.comment,   
        user.uid_imageurl, comments.comment_uid

                FROM post
                INNER JOIN user
                ON post.uid=user.uid
                LEFT JOIN comments
                ON comments.comment_pid=post.pid
                AND user.uid=comments.comment_uid
                ";

        $result = mysql_query($sql);



        while($row=mysql_fetch_assoc($result)){?>
        <ul>
            <li>User Profile image here:<? echo $row['uid_imageurl']; ?></li>
            <li>Post:<? echo $row['post']; ?></li>
            <li>Post by:<? echo $row['name']; ?></li>
            <li>Post images:<? echo $row['pid_imageurl']; ?></li>

            <li>post has: <? echo $row['likes']; ?> likes.</li>
            <li><? echo $row['comment']; ?></li>
            <li>by: <? echo $row['comment_uid']; ?></li>
           <!--This is only output as a stored id no rather than users name--!>




        </ul>


        <?}
        ?>

Answer 1

First, your query should be this:

SELECT 
    p.post, 
    p.pid_imageurl, 
    p.likes, 
    u.name, 
    c.comment,   
    u.uid_imageurl, 
    cu.name as CommentName
FROM 
    post p
    INNER JOIN user u ON 
        p.uid=u.uid
    LEFT JOIN comments c ON 
        c.comment_pid=post.pid
    left join user cu on
        c.comment_uid = cu.uid

And $row['comment_uid'] should become $row['CommentName'] .

Your original query is only grabbing comments that the original poster has made (your join condition). You want to join to the user table yet again to get the comment poster rather than the original poster.