the_tags() not working with custom query

Im using the following custom query to display a random post from a category in the sidebar:

<?php
		$querystr = "SELECT * FROM $wpdb->posts
		LEFT JOIN $wpdb->postmeta ON($wpdb->posts.ID = $wpdb->postmeta.post_id)
		LEFT JOIN $wpdb->term_relationships ON($wpdb->posts.ID = $wpdb->term_relationships.object_id)
		LEFT JOIN $wpdb->term_taxonomy ON($wpdb->term_relationships.term_taxonomy_id = $wpdb->term_taxonomy.term_taxonomy_id)
		WHERE $wpdb->term_taxonomy.term_id = 6 AND $wpdb->term_taxonomy.taxonomy = 'category'
		AND $wpdb->posts.post_status = 'publish'
		AND $wpdb->postmeta.meta_key = 'imagen'
		ORDER BY RAND() LIMIT 1";

		$pageposts = $wpdb->get_results($querystr, OBJECT);

		?>

	<?php if ($pageposts): ?>
	<?php foreach ($pageposts as $post): ?>

		<?php setup_postdata($post); ?>

From there on i continue.. with <h2><? the_title();... ?>' as usual, but if i try to use<? the_tags(); ?>` it doesn’t display anything, what shoul I do in order to display the tags?