如何获取最后一个请求日期，例如请求历史记录答案

【问题标题】：How to take the last Request date like a history of request如何获取最后一个请求日期，例如请求历史记录
【发布时间】：2014-07-03 07:44:48
【问题描述】：

我想从联合列中获取最后一个请求日期。我有这个代码来显示最后的请求日期：

;with cte 
as
(
    select
        [Date], [Badge id], Name, Reason, [Item1] item, 
        row_number() over (partition by [Badge id], [Item1] order by getdate()) rn
    from tbl_Request2
    where [Item1] Is Not null

    union

    select
        [Date], [Badge id], Name, Reason,[Item2] item,
        row_number() over (partition by [Badge id], [Item2] order by getdate()) rn
    from tbl_Request2 where [Item2] is not null union
)
Select
    T.[Badge ID], T.Name, T.Item, T.Reason, T. [Date] as [Current Request],
    ISNULL((Select top 1 [Date]
            from CTE
            where
                CTE.[Badge Id]=T.[Badge Id] and 
                CTE.[Item] = T.item and 
                CTE. [Date] < T. [Date]),T. [Date]) as [Last Requested] 
From CTE T 
order by [Badge ID]

它确实显示了最后一条记录，但不是预期的。它显示，例如：

2014 年 5 月 12 日 ID 001 请求 item1 THEN

ID 001 在 13/05/2014 再次请求 Item1 ；它显示最后请求的 12/05/2014 ；然后

ID 001 在 14/05/2014 再次请求 Item1 ；它显示最后请求的 12/05/2014 ； --> 这是错误我希望它显示 2014 年 13 月 5 日的最后一个请求

预期的表：

 ID   |  Items     |  Date        | Last Request Date
 001  |  Item1     |  12/05/2014  | 12/05/2014 --> lets say this is the first request of ID001
 002  |  Item2     |  25/04/2014  | 20/05/2014      
 001  |  Item1     |  13/05/2014  | 12/05/2014 --> It display the date of first requested     
 001  |  Item1     |  14/05/2014  | 13/05/2014 --> display the second request date

您对这个错误有什么建议吗？很抱歉再次发布它。我昨天已经问过这个问题了，但还是有一些错误。

提前致谢....

【问题讨论】：

标签： sql sql-server vb.net select union

【解决方案1】：

这有点尴尬。我问一个问题并自己回答。我只是意识到我的代码中缺少一些东西。我只需要删除前 1 并在我的代码中添加 max(date)。很抱歉问了我的错误。

;with cte 
as
(
    select
        [Date], [Badge id], Name, Reason, [Item1] item, 
        row_number() over (partition by [Badge id], [Item1] order by getdate()) rn
    from tbl_Request2
    where [Item1] Is Not null

    union

    select
        [Date], [Badge id], Name, Reason,[Item2] item,
        row_number() over (partition by [Badge id], [Item2] order by getdate()) rn
    from tbl_Request2 where [Item2] is not null union
)
Select
    T.[Badge ID], T.Name, T.Item, T.Reason, T. [Date] as [Current Request],
    ISNULL((Select max[Date] as [date]
            from CTE
            where
                CTE.[Badge Id]=T.[Badge Id] and 
                CTE.[Item] = T.item and 
                CTE. [Date] < T. [Date]),T. [Date]) as [Last Requested] 
From CTE T 
order by [Badge ID]

【讨论】：