Сумиране на поле от “Advanced Custom Fields” по дадена категория.

function get_cat_count_downloads_by_cat($cat_id){

global $wpdb;
$total_downloads = $wpdb->get_col($wpdb->prepare
("SELECT meta_value FROM wp_postmeta as pm
INNER JOIN wp_term_relationships as tr ON (pm.post_id = tr.object_id) 
INNER JOIN wp_term_taxonomy as tt ON (tr.term_taxonomy_id = tt.term_taxonomy_id) 
WHERE 1
AND tt.term_taxonomy_id = '".$cat_id."'
AND pm.meta_key = 'mp3_downloads'"));
	return array_sum( $total_downloads );
}