Consultar por mês/ano somando os valores

Simplismente não retorna nada!

<?php

$where = "WHERE (order_status_id = 10208) AND (order_status_id = 10207) AND (order_status_id = 10202) AND (order_status_id = 10204)";
$group = "GROUP BY MONTH(date_added), YEAR(date_added)";

$query = mysql_query("SELECT MONTH(date_added) + '.' + YEAR(date_added) AS periodo, SUM(total) AS valor FROM opencart_order $where $group");

while($ln=mysql_fetch_assoc($query)){

$periodo = $ln['periodo'];
$valor = $ln['valor'];

echo "$periodo - $valor";
}
 ?>