Diz blog

<?php 
$query="
SELECT $wpdb->posts.post_title, $wpdb->posts.guid, $wpdb->posts.ID , $wpdb->posts.comment_count
FROM  $wpdb->posts 
LEFT JOIN $wpdb->term_relationships ON ($wpdb->posts.ID = $wpdb->term_relationships.object_id) 
LEFT JOIN  $wpdb->term_taxonomy ON ($wpdb->term_taxonomy.term_taxonomy_id = $wpdb->term_relationships.term_taxonomy_id) 
LEFT JOIN $wpdb->terms ON ($wpdb->terms.term_id = $wpdb->term_taxonomy.term_id)
WHERE $wpdb->posts.ID <> $post->ID AND $wpdb->posts.post_status = 'publish' AND $wpdb->terms.term_id IN 
	(
	SELECT $wpdb->terms.term_id FROM  $wpdb->term_relationships
	LEFT JOIN  $wpdb->term_taxonomy ON ($wpdb->term_taxonomy.term_taxonomy_id = $wpdb->term_relationships.term_taxonomy_id) 
	LEFT JOIN $wpdb->terms ON ($wpdb->terms.term_id = $wpdb->term_taxonomy.term_id)
	WHERE $wpdb->term_relationships.object_id = $post->ID AND $wpdb->term_taxonomy.taxonomy='post_tag'
	)
 GROUP BY $wpdb->posts.ID ORDER BY RAND() LIMIT 3";
$related_posts = $wpdb->get_results($query); 
if ($related_posts) 
{
echo("<p>Схожие посты:</p>");
echo("<ul>");
foreach ($related_posts as $post) 
	{ 
	echo("<li><a href=\"".get_permalink($related_post->ID)."\" title=\"".$related_post->post_title."\">".$related_post->post_title."</a> (".$related_post->comment_count.")</li>");
	}
echo("</ul>"); 
}
?>