Mysql query returning too many rows - php

Question

so I have 3 tables all inner joined, I am trying to put discussions with the discussion topic on my main page, with the users name and the latest discussion message on the main page as well.
THE PROBLEM: The query is returning all messages attached to all the discussions.....I just need the last message associated with the discussion returned.
I have been at this all day and cant figure it out. I have tried group by but that just gave me an error on mysqli_fetch_array
Here is my code
$discussionquery = "SELECT discussion_messages.discussion_id, user_profile.first_name, user_profile.last_name, discussion_messages.message_text, case_discussion.discussion_title
FROM `user_profile`
INNER JOIN discussion_messages
ON (user_profile.user_id = discussion_messages.user_id)
INNER JOIN case_discussion
ON (case_discussion.discussion_id = discussion_messages.discussion_id)
WHERE discussion_messages.case_id = '$thecaseid'
ORDER BY discussion_messages.message_id DESC";
$discussionquerydata = mysqli_query($dbc, $discussionquery);
while ($row2 = mysqli_fetch_array($discussionquerydata)) {
$discussion_id = $row2['discussion_id'];
?>
<!-- Begin Recent Discussions -->
<div class="row">
<a href="discussion.php?newfact=$thecaseid'>">
<div class="col-xs-4 col-md-2">
<img src="img/client4.jpg" class="profile_picture img-rounded">
<?php echo '<h6 class="discussionname">' . $row2['first_name'] . ' ' . $row2['last_name'] . '</h6>';?>
</div>
</a>
<div class="col-xs-8 col-md-10 discussion_title">
<?php echo '<h5> '.$row2['discussion_title'].' -'. $row2['message_text'];?></h5>
<h6 class="pull-right">Dec. 25</h6>
</div>
</div>
<?php
};

Answer 1

You need logic to find the last message for each discussion. There is more than one way to write this condition.
The following does it using a not exists clause. This checks that there are no messages with a larger id for the discussion:
SELECT dm.discussion_id, up.first_name, up.last_name, dm.message_text, cd.discussion_title
FROM `user_profile` up INNER JOIN
discussion_messages dm
ON (user_profile.user_id = dm.user_id) INNER JOIN
case_discussion cd
ON (cd.discussion_id = dm.discussion_id)
WHERE dm.case_id = '$thecaseid' and
not exists (select 1
from discussion_messages dm2
where dm2.discussion_id = dm.discussion_id and
dm2.message_id > dm.message_id
)
ORDER BY dm.message_id DESC;

Answer 2

One suggestion, use table aliases. The amount of total code will be smaller and easier to understand. Use the limit clause to return 1 row.
$discussionquery = "
SELECT
m.discussion_id,
u.first_name,
u.last_name,
d.message_text,
c.discussion_title
FROM `user_profile` as u
INNER JOIN discussion_messages as m
ON (u.user_id = m.user_id)
INNER JOIN case_discussion c
ON (m.discussion_id = c.discussion_id)
WHERE
m.case_id = '$thecaseid'
ORDER BY
m.message_id DESC
LIMIT 1";