having duplicate tags ignored in only one query_post

Hi I have a question regarding tags in query_post.

My goal is to have all tags used in a query echoed but I don’t want the same tag echoed more the once.

I was thinking of the duplicate post technique but it needs two queries.

It could have to do with the way I am querying as well… maybe needs arrays and variables… it’s getting a touch out of my wp understanding…

I am sure there’s a way to kill a duplicate entry so can somebody help me out or give me a lead to a similar problem that was resolved?

Thanks heaps,
Brian

<ul id="filter">
<?php query_posts("posts_per_page=-1&amp;cat=5");?>
<?php if (have_posts()) : while (have_posts()) : the_post(); ?>
<?php
global $post;
if ( has_tag() ) { ?>
<li><a href="#"><?php
$posttags = get_the_tags();
if ($posttags) {
foreach($posttags as $tag) {
echo $tag->name . '';
}
}
?></a></li>
<?php } else {

}?><?php endwhile; ?><?php endif; ?>
</ul>