Question

我想做一个像这样的人类似的事情： T-SQL Subquery Max(Date) and Joins

我必须用n：m关系来做这件事。

所以布局是：

tbl_Opportunity
tbl_Opportunity_tbl_OpportunityData
tbl_OpportunityData

所以当你看到有一个交叉表连接机会与opportunitydata。每个机会都有多个机会数据。在我看来，我只想要一个包含所有机会的列表和来自最新机会数据的数据。

我试过这样的事情：

SELECT     
    dbo.tbl_Opportunity.Id, dbo.tbl_Opportunity.Subject, 
    dbo.tbl_User.UserName AS Responsible, dbo.tbl_Contact.Name AS Customer, 
    dbo.tbl_Opportunity.CreationDate, dbo.tbl_Opportunity.ActionDate AS [Planned Closure], 
    dbo.tbl_OpportunityData.Volume, 
    dbo.tbl_OpportunityData.ChangeDate, dbo.tbl_OpportunityData.Chance
FROM         
    dbo.tbl_Opportunity 
INNER JOIN
    dbo.tbl_User ON dbo.tbl_Opportunity.Creator = dbo.tbl_User.Id 
INNER JOIN
    dbo.tbl_Contact ON dbo.tbl_Opportunity.Customer = dbo.tbl_Contact.Id 
INNER JOIN
    dbo.tbl_Opprtnty_tbl_OpprtnityData ON dbo.tbl_Opportunity.Id = dbo.tbl_Opprtnty_tbl_OpprtnityData.Id 
INNER JOIN
    dbo.tbl_OpportunityData ON dbo.tbl_Opprtnty_tbl_OpprtnityData.Id2 = dbo.tbl_OpportunityData.Id

问题是我的视图现在包含每个机会数据的行，因为我不知道如何过滤我只想要最新的数据。

你能帮帮我吗？我的问题描述是否足够清楚？

提前谢谢:-) 最好的祝愿，月桂精

Answer 1

; WITH Base AS (
    SELECT     dbo.tbl_Opportunity.Id, dbo.tbl_Opportunity.Subject, dbo.tbl_User.UserName AS Responsible, dbo.tbl_Contact.Name AS Customer, 
                      dbo.tbl_Opportunity.CreationDate, dbo.tbl_Opportunity.ActionDate AS [Planned Closure], dbo.tbl_OpportunityData.Volume, 
                      dbo.tbl_OpportunityData.ChangeDate, dbo.tbl_OpportunityData.Chance
    FROM         dbo.tbl_Opportunity INNER JOIN
                      dbo.tbl_User ON dbo.tbl_Opportunity.Creator = dbo.tbl_User.Id INNER JOIN
                      dbo.tbl_Contact ON dbo.tbl_Opportunity.Customer = dbo.tbl_Contact.Id INNER JOIN
                      dbo.tbl_Opprtnty_tbl_OpprtnityData ON dbo.tbl_Opportunity.Id = dbo.tbl_Opprtnty_tbl_OpprtnityData.Id INNER JOIN
                      dbo.tbl_OpportunityData ON dbo.tbl_Opprtnty_tbl_OpprtnityData.Id2 = dbo.tbl_OpportunityData.Id    
)

, OrderedByDate AS (
    SELECT *, ROW_NUMBER() OVER (PARTITION BY Id ORDER BY ChangeDate DESC) RN FROM Base
)

SELECT * FROM OrderedByDate WHERE RN = 1

为了使其更具可读性，我正在使用CTE（WITH部分）。最后，真正的“技巧”是ROW_NUMBER()按tbl_Opportunity.Id对数据进行分区，然后按ChangeDate DESC排序分区（我称之为RN）。显然，每个分区的最大日期为RN = 1，然后我们按RN过滤。

如果不使用CTE，它将是这样的：

SELECT * FROM (
    SELECT     dbo.tbl_Opportunity.Id, dbo.tbl_Opportunity.Subject, dbo.tbl_User.UserName AS Responsible, dbo.tbl_Contact.Name AS Customer, 
                      dbo.tbl_Opportunity.CreationDate, dbo.tbl_Opportunity.ActionDate AS [Planned Closure], dbo.tbl_OpportunityData.Volume, 
                      dbo.tbl_OpportunityData.ChangeDate, dbo.tbl_OpportunityData.Chance,
                      ROW_NUMBER() OVER (PARTITION BY dbo.tbl_Opportunity.Id ORDER BY dbo.tbl_OpportunityData.ChangeDate DESC) RN
    FROM         dbo.tbl_Opportunity INNER JOIN
                      dbo.tbl_User ON dbo.tbl_Opportunity.Creator = dbo.tbl_User.Id INNER JOIN
                      dbo.tbl_Contact ON dbo.tbl_Opportunity.Customer = dbo.tbl_Contact.Id INNER JOIN
                      dbo.tbl_Opprtnty_tbl_OpprtnityData ON dbo.tbl_Opportunity.Id = dbo.tbl_Opprtnty_tbl_OpprtnityData.Id INNER JOIN
                      dbo.tbl_OpportunityData ON dbo.tbl_Opprtnty_tbl_OpprtnityData.Id2 = dbo.tbl_OpportunityData.Id    
) AS Base WHERE RN = 1

Answer 2

该声明可以进一步简化：

SELECT TOP 1 WITH TIES
    dbo.tbl_Opportunity.Id, dbo.tbl_Opportunity.Subject, dbo.tbl_User.UserName AS Responsible, 
    dbo.tbl_Contact.Name AS Customer, dbo.tbl_Opportunity.CreationDate, 
    dbo.tbl_Opportunity.ActionDate AS [Planned Closure], dbo.tbl_OpportunityData.Volume, 
    dbo.tbl_OpportunityData.ChangeDate, dbo.tbl_OpportunityData.Chance
FROM 
    dbo.tbl_Opportunity INNER JOIN
    dbo.tbl_User ON dbo.tbl_Opportunity.Creator = dbo.tbl_User.Id INNER JOIN
    dbo.tbl_Contact ON dbo.tbl_Opportunity.Customer = dbo.tbl_Contact.Id INNER JOIN
    dbo.tbl_Opprtnty_tbl_OpprtnityData ON dbo.tbl_Opportunity.Id = dbo.tbl_Opprtnty_tbl_OpprtnityData.Id INNER JOIN
    dbo.tbl_OpportunityData ON dbo.tbl_Opprtnty_tbl_OpprtnityData.Id2 = dbo.tbl_OpportunityData.Id    
ORDER BY 
    ROW_NUMBER() OVER (PARTITION BY dbo.tbl_Opportunity.Id ORDER BY dbo.tbl_OpportunityData.ChangeDate DESC);

内部联接的最新日期的T-SQL子查询

2 个答案: