第一步：对OrderItems表进行分组求和，并得到一张新表n 第二步：对Customers、Orders、新表n三张表进行连接查询 第三步：排一下序 select c.cust_name,o.order_num,n.OrderTotal from Customers c,Orders o,(select order_num,sum(quantity*item_price) OrderTotal from OrderItems group by order_num) n where c.cust_id=o.cust_id and o.order_num=n.order_num order by...