SQL 查询以查找最近的一组记录 [英] SQL Query to find the most recent group of records

问题描述

我有共享 IdString 的记录历史记录(每次更新的多条记录都具有完全相同的日期时间).

I have a history of records (multiple records per update all with the exact same datetime) that share an IdString.

我想要一个查询来确定这些记录中的哪些是最近更新组的一部分.

I want a query to determine which of these records are part of the most recent update group.

此查询将向我显示一个具有最新更新日期的记录，但是对于每个分区，我需要具有该最大日期的所有记录..>

This query will show me one of the records having the most recent update date, but for each partition, I need all the records with that max date.

;with cte as(
select ROW_NUMBER() over (partition by IdString order by UpdateDate desc) as [rn], *
from MyTable
)
select  CASE WHEN (cte.rn = 1) THEN 0 ELSE 1 END [IsOld], *
from MyTable m
inner join cte on cte.RecordId= m.RecordId

有人可以帮我找出合适的查询吗?

Would someone please help me figure out an appropriate query?

示例

(IsOld is the desired calculated value)

IsOld RecordId  IdString  UpdateDate
1         1     ABC 2011-06-16 
1         2     ABC 2012-05-30 
1         3     ABC 2008-12-31 
0         4     ABC 2012-06-08 
1         5     ABC 2011-01-16 
0         6     ABC 2012-06-08 
1         7     ABC 2012-06-07 
1         8     XYZ 2001-01-16
1         9     XYZ 2013-01-30
0         10    XYZ 2001-01-31
1         11    XYZ 2013-06-01
1         12    XYZ 2001-05-04
0         13    XYZ 2013-01-30

推荐答案

试试这个 -

;WITH cte AS(
    SELECT RANK() OVER(PARTITION BY IdString ORDER BY UpdateDate DESC) AS [row_num], *
    FROM   MyTable
)
SELECT CASE WHEN m.[row_num] = 1 THEN 0 ELSE 1 END isOld, *
from cte m

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