sql - 如何在sql中使用三个表的子查询

Question

我有三个表，例如:

客户表

CUSTOMER#   LASTNAME    FIRSTNAME
1001    MORALES         BONITA
1002    THOMPSON        RYAN
1003    SMITH           LEILA
1004    PIERSON         THOMAS
1005    GIRARD          CINDY

订单表

ORDER#  CUSTOMER#   ORDERDATE
1000    1005    31/MAR/09
1001    1010    31/MAR/09
1002    1011    31/MAR/09
1003    1001    01/APR/09

orderitems 表

ORDER#  ITEM#   ISBN    QUANTITY
1000    1   3437212490  1
1001    1   9247381001  1
1001    2   2491748320  1
1002    1   8843172113  2

我的问题是:如何打印订购超过 1 件商品的客户姓名(数量超过 1？

我的sql查询是这样的:

SELECT c.firstname, c.lastname
FROM customers c
WHERE (SELECT o.quantity FROM orderitems WHERE o.quantity > 1) 

上面的查询有什么错误？

Answer 1

这应该可以做到:

select c.firstname, c.lastname
from customer c
    join orders o on c.customer# = o.customer#
    join orderitems oi on o.order# = oi.order#
group by c.firstname, c.lastname
having sum(oi.quantity) > 1