Question

我正在尝试基于W3Schools.com SQL数据库解决此问题。到目前为止，我想出了以下内容，其中显示了之前订购相同产品的客户的客户名称和产品。我在订购客户订购的相同产品的总数方面存在问题。

select customername, products.productid, productname
from orderdetails, orders, customers, products
where orderdetails.orderid=orders.orderid AND
      orders.customerid=customers.customerid AND
      orderdetails.productid=products.productid
group by customername, products.productid, productname
HAVING COUNT(*) > 1
order by customername;

Answer 1

您已经拥有了客户的结果查询。将其移动到子查询并加入自身

SELECT *
FROM 
   (select customername, products.productid, productname, COUNT(*) as cnt
    from orderdetails, orders, customers, products
    where orderdetails.orderid=orders.orderid AND
          orders.customerid=customers.customerid AND
          orderdetails.productid=products.productid
    group by customername, products.productid, productname
    HAVING COUNT(*) > 1) c1 
    INNER JOIN 
    (select customername, products.productid, productname, COUNT(*) as cnt
      from orderdetails, orders, customers, products
      where orderdetails.orderid=orders.orderid AND
            orders.customerid=customers.customerid AND
            orderdetails.productid=products.productid
      group by customername, products.productid, productname
      HAVING COUNT(*) > 1) c2 
    ON c1.productId=c2.productId and c1.productname=c2.productname

order by c1.customername

对于之前订购过相同产品的客户，请显示订购相同产品的客户名称，产品和总数

1 个答案: