Fetch taxonomy terms statistics for all posts before due date, with a single database query.

functions.php

/**
 * Fetch taxonomy terms statistics for all posts before due date, with a single database query.
 * 
 * Assumes that the 'due' values are saved as YYYYMMDD
 *
 * @see http://www.wpquestions.com/question/showChronoLoggedIn/id/9770
 * @param string $taxonomy
 * @param string $meta_key
 * @return mixed Database query results
 * @version 0.0.2
 */


function get_tax_terms_stats_before_due_date( $taxonomy, $meta_key )
{
        global $wpdb;
                
        $sql ="
                SELECT COUNT(1) as postscount, t.term_id, t.name, t.slug, tt.taxonomy
                FROM tfl_term_relationships tr
                        INNER JOIN {$wpdb->posts}          p  ON p.ID = tr.object_id
                        INNER JOIN {$wpdb->postmeta}       pm ON ( p.ID = pm.post_id AND pm.meta_key = '%s' )
                        INNER JOIN {$wpdb->term_taxonomy}  tt ON tr.term_taxonomy_id = tt.term_taxonomy_id
                        INNER JOIN {$wpdb->terms}          t ON tt.term_id = t.term_id
                WHERE
  	             	 1*pm.meta_value > %d
                        AND p.post_status = 'publish'
                        AND tt.taxonomy = '%s'
                GROUP BY t.term_id
                ORDER BY postscount DESC
        ";
        return $wpdb->get_results( $wpdb->prepare( $sql, $meta_key, date( 'Ymd' ), $taxonomy ) );
}