sql-server - T-SQL 获取给定组的最后一个值

Question

我正在尝试获取一组值(分区)中的最后一个值，但遇到了一些麻烦。在下面的示例中，您可以看到我正在使用的示例数据集。 MAX() 不起作用，因为这里的“最后一个”是分区 (ID) 中最后一个日期的日期。我在下面的查询中注释掉了 LAST_VALUE ，但这似乎也不起作用......不确定我做错了什么。我想要的是这样的结果数据集:

create table #Example (ID int, [Date] datetime, Rating tinyint)

insert into #Example (ID, [Date], Rating)
values
    (5227,  '2021-01-11 19:21:39.107',  1)
    ,(128,  '2020-06-16 17:32:15.653',  5)
    ,(128,  '2020-06-23 11:35:16.570',  1)
    ,(2038, '2020-09-14 13:13:48.253',  2)
    ,(1268, '2020-07-30 16:05:07.950',  0)
    ,(2398, '2020-09-30 13:51:21.813',  5)
    ,(2058, '2020-09-14 13:13:48.253',  1)
    ,(3396, '2020-11-05 12:04:16.043',  5)
    ,(3396, '2020-12-07 13:23:05.357',  3)
    ,(3148, '2020-11-05 12:04:16.043',  1)
    ,(3399, '2020-11-06 12:04:16.043',  2)
    ,(3399, '2020-12-08 13:23:05.357',  4)

select
    exm.ID
    , exm.Date
    , exm.Rating
    --, LAST_VALUE(exm.Rating) over (partition by exm.ID order by exm.Date) as [FinalRating]
from 
    #Example as exm

drop table #Example

如果您有任何帮助，我将不胜感激!

Answer 1

也许对您的查询稍加修改就会起作用:

create table #Example (ID int, [Date] datetime, Rating tinyint)

insert into #Example (ID, [Date], Rating)
values
    (5227,  '2021-01-11 19:21:39.107',  1)
    ,(128,  '2020-06-16 17:32:15.653',  5)
    ,(128,  '2020-06-23 11:35:16.570',  1)
    ,(2038, '2020-09-14 13:13:48.253',  2)
    ,(1268, '2020-07-30 16:05:07.950',  0)
    ,(2398, '2020-09-30 13:51:21.813',  5)
    ,(2058, '2020-09-14 13:13:48.253',  1)
    ,(3396, '2020-11-05 12:04:16.043',  5)
    ,(3396, '2020-12-07 13:23:05.357',  3)
    ,(3148, '2020-11-05 12:04:16.043',  1)
    ,(3399, '2020-11-06 12:04:16.043',  2)
    ,(3399, '2020-12-08 13:23:05.357',  4)

select
    exm.ID
    , exm.Date
    , exm.Rating
    , last_value(exm.Rating) over (partition by exm.id order by exm.date
                                          rows between current row and unbounded following) as [FinalRating]
from 
    #Example as exm
order by id, date