Display tags from a specific category and sort them

I am currently creating a theme wherein there are two lines on navigation (top and subnav). The top layer lists the categories, and the subnav appears when you hover over a top level menu item. The sub nav then displays tags from the category in the top menu.

In order to do this I required a custom query which loads the tags for a specific category [taken from this thread]

So in my functions I have this code:

function get_category_tags($args) {
	global $wpdb;
	$tags = $wpdb->get_results
	("
		SELECT DISTINCT terms2.term_id as tag_id, terms2.name as tag_name, null as tag_link
		FROM
			wp_posts as p1
			LEFT JOIN wp_term_relationships as r1 ON p1.ID = r1.object_ID
			LEFT JOIN wp_term_taxonomy as t1 ON r1.term_taxonomy_id = t1.term_taxonomy_id
			LEFT JOIN wp_terms as terms1 ON t1.term_id = terms1.term_id,

			wp_posts as p2
			LEFT JOIN wp_term_relationships as r2 ON p2.ID = r2.object_ID
			LEFT JOIN wp_term_taxonomy as t2 ON r2.term_taxonomy_id = t2.term_taxonomy_id
			LEFT JOIN wp_terms as terms2 ON t2.term_id = terms2.term_id

		WHERE
			t1.taxonomy = 'category' AND p1.post_status = 'publish' AND terms1.term_id IN (".$args['categories'].") AND
			t2.taxonomy = 'post_tag' AND p2.post_status = 'publish'
			AND p1.ID = p2.ID
		ORDER BY tag_name
	");
	$count = 0;
	foreach ($tags as $tag) {
		$tags[$count]->tag_link = get_tag_link($tag->tag_id);
		$count++;
	}
	return $tags;
}

and in my theme I simply use this to output and style the tags:

<?php $args = array( 'categories' => '5' ); $tags = get_category_tags($args); ?>
				<!-- echo and style tags -->
				<?php 	$content .= "<span>";
						foreach ($tags as $tag) {
						$even_odd = ( 'odd' != $even_odd ) ? 'odd' : 'even';
						$content .= "<a href=\"$tag->tag_link\" class=\"$even_odd\">$tag->tag_name</a>  |"; }
						$content .= "</span>";
						echo $content;
				?>

However, is there anyway I can modify this code so it outputs the tags in order of how many posts each tag has? I’m not overly familiar with SQL, but I believe I want to change the ORDER BY in my functions.php to sort by wp_term_taxonomy.count. Could anyone point me in the right direction?

Thanks.