select o.cust_id, -- 选择Orders表中的顾客ID sum(oi.item_price * oi.quantity) as total_ordered -- 计算每个顾客所有订单的总金额 from Orders o join OrderItems oi on oi.order_num = o.order_num -- 通过订单号将Orders表和OrderItems表进行连接 group by o.cust_id -- 按照顾客ID对结果进行分组,以便为每个顾客计算总金额 order by total_order...