where a.productNo = c.productNo and b.orderNo = c.orderNo and productName = '52倍速光驱') and customerNo in( select customerNo
from Product a, OrderMaster b, OrderDetail c where a.productNo = c.productNo and b.orderNo = c.orderNo and productName = '17寸显示器' )
16.求每位客户订购的每种商品的总数量及平均单价，并按客户编号、商品号从小到大排列
select distinct b.customerNo 客户编号, productNo 商品号, sum(quantity) 总数量, avg(price) 平均单价 from OrderDetail a, customer b, OrderMaster c where a.orderNo = c.orderNo and b.customerNo =
c.customerNo
group by b.customerNo, productNo order by b.customerNo, productNo
