Question

This query outputs each result 6 times: So, for one row with a body of ‘ayo’, it will be outputted as: ayo
ayo
ayo
ayo
ayo
ayo

function get_comments($page_type, $spot) {
        $query = mysql_query("
                              SELECT
                              comments.user_id AS user_id,
                              comments.page_type AS page_type,
                              comments.spot AS spot,
                              comments.comment AS comment,
                              comments.timestamp AS timestamp,
                              users.first_name AS first_name,
                              users.last_name AS last_name
                              FROM comments, users
                              WHERE page_type = '$page_type' AND spot = '$spot' AND (comments.user_id = users.user_id OR comments.user_id = '0')
                              ORDER BY timestamp DESC
                             ");

        while($fetch = mysql_fetch_assoc($query)) {

            $comment = $fetch['comment'];
            $timestamp = $fetch['timestamp'];
            $timestamp_date = date('M d y\'', $timestamp);
            $timestamp_time = date('g:m', $timestamp);
            $comments_user_id = $fetch['user_id'];

                if(date('H', $timestamp) > 12) {
                    $am_pm = 'pm';
                    } else {
                        $am_pm = 'am';
                        }

            $first_name = $fetch['first_name'];
            $last_name = $fetch['last_name'];

            ?>

            <div id="replies">

                <?php if($comments_user_id == '0') {echo 'Guest';} else { echo $first_name.' '.$last_name; } ?><br />
                <?php echo $timestamp_date; ?><br />
                <?php echo $comment; ?>

            </div>

            <?php

            }
        }

In here $page_type and $spot refer to: http://localhost/$page_type/$spot

Answer 1

You’re getting duplicates because your implicit join condition contains this:

OR comments.user_id = '0'

and you have multiple rows with comments.user_id = 0. Each of these user_id = 0 rows will appear match your join condition and that will lead to duplicates. The solution is to fix your data so that each comment has a valid user_id where “valid” means “has an entry in users” and the drop the comments.user_id = 0 part of your join condition. And while you’re at it, switch to InnoDB tables and add foreign keys to enforce this referential integrity constraint.

BTW, if user_id is an integer then you really shouldn’t be quoting it; you’re making the database do unnecessary work and building a bad habit that will cause you some pain and suffering if you every use another database. You should also switch to an explicit join:

from comments join users on comments.user_id = users.id
where page_type = '$page_type' and spot = '$spot'