SELECT o.*, CONCAT(u.user_name, u.user_name2) as customer_name, 
(SELECT SUM(item_price * item_count) FROM genexis_orders_items li WHERE li.`id_order` = o.id ) as price_total FROM `genexis_orders` o 
JOIN genexis_user u ON u.id = o.`id_customer` 
WHERE o.`closed` = 0