题解 | #返回顾客名称和相关订单号以及每个订单的总价#

select Customers.cust_name , OrderItems.order_num,
sum(OrderItems.quantity*OrderItems.item_price) from OrderItems join
Orders  
on OrderItems.order_num = Orders.order_num
join  Customers  on  Orders.cust_id = Customers.cust_id
group by Customers.cust_name , OrderItems.order_num
order by Customers.cust_name , OrderItems.order_num

1、多张表联合查询，a join b on 添加1 join c on 添加2

2、聚合函数查询一般联合group by

3、顺序 order by