Question

使用此查询，我得到每个客户放置了多少订单的结果。但是，当我在SELECT字段中使用SUM（OrderLine.ActualPrice）并使用内部联接将Order表链接到包含价格的OrderLine表时。 COUNT结果是倾斜的，因为OrderLine表包含同一订单的多个OrderNo，因为一个订单可以包含多个产品。

如何将COUNT保留在此查询的结果中，同时为订单的总购买金额添加SUM查询？

SELECT C.custno, 
       companyname, 
       Count(customerorder.orderno)AS 'Total Orders', 
FROM   customer C 
       INNER JOIN customerorder 
               ON customerorder.custno = C.custno 
GROUP  BY C.custno, 
          companyname

具有不正确结果的修改查询

SELECT C.custno, 
       companyname, 
       Count(customerorder.orderno)AS 'Total Orders', 
       Sum(orderline.actualprice) 
FROM   customer C 
       INNER JOIN customerorder 
               ON customerorder.custno = C.custno 
       INNER JOIN orderline 
               ON customerorder.orderno = orderline.orderno 
GROUP  BY C.custno, 
          companyname

这是我尝试使用的查询，并收到了倾斜的COUNT个结果。

Answer 1

您有两个基本选项。

使用DISTINCT

SELECT C.custno, 
       companyname, 
       Count(DISTINCT customerorder.orderno)AS 'Total Orders', 
       Sum(orderline.actualprice) 
FROM   customer C 
       INNER JOIN customerorder 
               ON customerorder.custno = C.custno 
       INNER JOIN orderline 
               ON customerorder.orderno = orderline.orderno 
GROUP  BY C.custno, 
          companyname

注意：的

在对另一个问题的评论中，你说这个结果仍然存在。这似乎意味着相同的orderno可以出现在多个customerorder记录中。这是对的吗？

使用子查询将联接设置为1：1而不是1：多

SELECT C.custno, 
       companyname, 
       Count(customerorder.orderno)AS 'Total Orders', 
       Sum(orderline.actualprice) 
FROM   customer C 
       INNER JOIN customerorder 
               ON customerorder.custno = C.custno 
       INNER JOIN (SELECT orderno, SUM(actualprice) AS actualprice
                     FROM orderline 
                 GROUP BY orderno)
               ON customerorder.orderno = orderline.orderno 
GROUP  BY C.custno, 
          companyname

Answer 2

试试这个

SELECT C.custno, 
       companyname, 
       Count(Distinct customerorder.orderno)AS 'Total Orders', 
       Sum(orderline.actualprice) 
FROM   customer C 
       INNER JOIN customerorder 
               ON customerorder.custno = C.custno 
       INNER JOIN orderline 
               ON customerorder.orderno = orderline.orderno 
GROUP  BY C.custno, 
          companyname

在DISTINCT订单号上使用Count

SUM干扰COUNT

2 个答案: