多个表列上的 SQL Server 索引

Question

我编写了一个使用两列的查询，每列都来自不同的表。如何为这些列建立索引，甚至有可能吗？

select countryName, balance
from main.country c 
join main.person p on (c.countryId = p.countryId)
where balance = (select MAX(balance) 
                 from main.person p2 
                 join main.country c2 on (c2.countryId = p2.countryId)
                 where c.countryId = c2.countryId 
                   and p.countryId = p2.countryId)
order by countryName;

Answer 1

在 SQL Server 中，如果您想为来自不同表的列创建索引，则可以创建 Schema Bound View 并在该视图之上构建索引。

在你的情况下，创建一个模式绑定视图：

CREATE VIEW MyBoundView
WITH SCHEMABINDING  
AS  
   -- YOU QUERY 
   select countryName, balance
   from main.country c join main.person p on(c.countryId=p.countryId)
   where balance=(select MAX(balance) from main.person p2 join main.country c2 
   on(c2.countryId=p2.countryId)
   where c.countryId=c2.countryId and p.countryId=p2.countryId)
   order by countryName;  

GO  

现在您可以在此绑定视图上使用您的两列创建索引：

--Example index on the bound view.  
CREATE UNIQUE CLUSTERED INDEX IDX_V1   
   ON MyBoundView (countryName, balance);  
GO  

您可能会发现this article 很有用。

Answer 2

这是您的查询：

select countryName, balance
from main.country c join
     main.person p
     on c.countryId = p.countryId
where balance = (select MAX(balance)
                 from main.person p2 join
                      main.country c2
                      on c2.countryId = p2.countryId
                 where c.countryId = c2.countryId and p.countryId = p2.countryId
                )
order by countryName;

据我所知，您想要每个国家/地区的最高余额，以及重复项（如果有）。您可以使用以下方法获得这些：

select top (1) with ties c.countryName, p.balance
from main.country c join
     main.person p
     on c.countryId = p.countryId
order by rank() over (partition by c.countryId order by p.balance desc);

要按国家/地区名称排序，您需要一个子查询：

select cp.*
from (select top (1) with ties c.countryName, p.balance
      from main.country c join
           main.person p
           on c.countryId = p.countryId
      order by rank() over (partition by c.countryId order by p.balance desc)
     ) cp
order by countryName;