Question

我有一个音乐商店的数据库，我需要提取特定于每个国家/地区的客户的最大购买价值。使用MAX函数时，我注意到在“ United Kingdom”中有两个最大值的联系。因此，我需要查询以返回该国家/地区的两个客户。

With t1 As (
           Select i.CustomerId, c.FirstName, c.LastName, 
                      i.BillingCountry Country, Sum(i.Total) Totals
             From Invoice i
              Join Customer c
              On c.CustomerId = i.CustomerId
             GROUP BY 1, 4)

Select CustomerId, FirstName, LastName, Country, Max(Totals) TotalSpent
    From t1
    Group By 4;

这是输出

这应该是输出

我尝试使用TOP，但显然按工作区，它不接受此功能。因此，请提出一种不使用此功能的解决方案。

谢谢。

Answer 1

我会考虑类似的东西

With t1 As (
           Select i.CustomerId, c.FirstName, c.LastName, 
                      i.BillingCountry Country, Sum(i.Total) Totals
             From Invoice i
              Join Customer c
              On c.CustomerId = i.CustomerId
             GROUP BY 1, 4)

Select CustomerId, FirstName, LastName, Country, Totals TotalSpent
    From t1
    WHERE t1.Total = (SELECT MAX(Totals) FROM t1 t2 WHERE t1.Country = t2.Country)
    Group By 4;

（我在主查询的MAX(Totals)语句中将Totals更改为SELECT，并添加了WHERE子句）

或

With t1 As (
           Select i.CustomerId, c.FirstName, c.LastName, 
                      i.BillingCountry Country, Sum(i.Total) Totals
             From Invoice i
              Join Customer c
              On c.CustomerId = i.CustomerId
             GROUP BY 1, 4),
t2 as (
 SELECT Country, MAX(Totals) as Totals
 FROM t1
 GROUP BY Country
)
Select t1.CustomerId, t1.FirstName, t1.LastName, t1.Country, t1.Totals TotalSpent
    From t1 INNER JOIN t2
     on t1.Country = t2.Country and t1.Totals = t2.Totals
    Group By 4;

（我添加了t2 CTE，将其加入到您的主查询中，并相应地调整了主SELECT）

在两种情况下，我都试图选择所有客户信息，其中该客户的总数等于其所在国家/地区的最大总数。原则上，无论有多少关系，这都应该起作用。

Answer 2

使用窗口功能！

select CustomerId, FirstName, LastName, 
       Country, Totals
from (select i.CustomerId, c.FirstName, c.LastName, 
             i.BillingCountry as Country, sum(i.Total) as Totals,
             rank() over (partition by i.BillingCountry over sum(i.Total) desc) as seqnum
      from Invoice i join
           Customer c
           on c.CustomerId = i.CustomerId
      group by i.CustomerId, c.FirstName, c.LastName, 
               i.BillingCountry
     ) ic
where seqnum = 1;

如何在查询中获得两条最大值的关系？

2 个答案: