使用SQL查询查找订购> x类产品的客户的详细信息

Question

请注意,我在这里看到过类似的查询,但认为我的查询不同,值得单独提问.

假设有一个包含以下表的数据库:

1. customer_table with customer_ID(key field),customer_name
2. order_table with order_ID(key field),customer_ID,product_ID

现在假设我想找到订购了10种以上不同类型产品的所有客户的名称,以及他们订购的产品类型的数量.同一产品的多个订单不计算在内.

我认为下面的查询应该有效,但有以下问题:

1. 使用count(distinct xxx)通常是否允许使用"group by"语句？
2. 我使用标准方法的方法是什么？有没有人有更好的想法(例如没有涉及临时表)？

以下是我的查询

select T1.customer_name, T1.customer_ID, T2.number_of_products_ordered
from customer_table T1
inner join 
(
    select cust.customer_ID as customer_identity, count(distinct ord.product_ID) as number_of_products_ordered
    from customer_table cust
    inner join order_table ord on cust.customer_ID=ord.customer_ID
    group by ord.customer_ID, ord.product_ID
    having count(distinct ord.product_ID) > 10
) T2
on T1.customer_ID=T2.customer_identity
order by T2.number_of_products_ordered, T1.customer_name

Answer 1

这不是你想要的吗？似乎有点简单.在SQL Server上测试它 - 工作正常.

SELECT customer_name, COUNT(DISTINCT product_ID) as products_count FROM customer_table
INNER JOIN orders_table ON customer_table.customer_ID = orders_table.customer_ID
GROUP BY customer_table.customer_ID, customer_name
HAVING COUNT(DISTINCT product_ID) > 10