the submitted query of this contr has an error ?!

$net_total_query = tep_db_query( "SELECT SUM( value ) AS total FROM orders_total WHERE orders_id IN ( SELECT orders_id FROM orders WHERE year( date_purchased ) = " . $years['y'] . " AND month( date_purchased ) = " . $months['m'] . " ) AND class = 'ot_subtotal'" );
$net_total = tep_db_fetch_array( $net_total_query );

More...