Last row still shows <div> - php

Question

I'm learning PHP/MySQLi at the minute and I need help with something I just can't seem to find online. I am using <div class="hr"> </div> after every topic in the forum script I am making but I don't want it to display one after the last topic their is, how do I stop my script from displaying it after the last row? I would be grateful for any help and just so I'm a 100% clear.
Here is how it looks:
Topic Title Here
-------------------------------------
Topic Title Here
-------------------------------------
But I want:
Topic Title Here
-------------------------------------
Topic Title Here
My code of where this part is:
<?php
}
$dn2 = mysql_query('select t.id, t.title, t.authorid, u.username
as author,
count(r.id) as replies from topics as t left join topics as r on
r.parent="'.$id.'"
and r.id=t.id and r.id2!=1 left join users as u on u.id=t.authorid
where t.parent="'.$id.'" and t.id2=1 group by t.id order by t.timestamp2 desc');
if(mysql_num_rows($dn2)>0)
{
?>
<table id="main-table">
<tr>
<td id="side">
</td>
<td id="content">
<?php
while($dnn2 = mysql_fetch_array($dn2))
{
?>
<div><a href="read_topic.php?id=<?php echo $dnn2['id']; ?>">
<?php echo htmlentities($dnn2['title'], ENT_QUOTES, 'UTF-8'); ?></a>
- <a class="wtb" href="profile.php?id=<?php echo $dnn2['authorid']; ?>">
<?php echo htmlentities($dnn2['author'], ENT_QUOTES, 'UTF-8'); ?></a></div>
<div class="hr"> </div>
<?php
}
?>

Answer 1

Without seeing your code, an easy way to fix it would be to draw the line first unless it's the first topic
if ($topicNumber != 1) echo ('<div class="hr"> </div>');
<div><?php echo $dnn1['topic']; ?><div>
<? } ?>

Answer 2

You can handle this easily with your css:
<style>
.wrapper div {border-bottom: 1px dashed black}
.wrapper div:last-child{ border-bottom: 0}
</style>
<div class="wrapper">
<div><?php echo $dnn1['topic']; ?><div>
<? } ?>
</div>