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问题描述
我有一个包含以下各列的表
I have a table that has the following columns
- 编号
- ForeignKeyId
- AttributeName
- AttributeValue
- 已创建
一些数据可能看起来像这样:
Some of the data may look like this:
1, 1, 'EmailPreference', 'Text', 1/1/2010
2, 1, 'EmailPreference', 'Html', 1/3/2010
3, 1, 'EmailPreference', 'Text', 1/10/2010
4, 2, 'EmailPreference', 'Text', 1/2/2010
5, 2, 'EmailPreference', 'Html', 1/8/2010
我想运行一个查询，该查询使用Created列来确定每个不同的ForeignKeyId和AttributeName的AttributeValue列的最新值.输出示例为:
I'd like to run a query that pulls the most recent value of the AttributeValue column for each distinct ForeignKeyId andAttributeName, using the Created column to determine the most recent value. Example output would be:
ForeignKeyId AttributeName AttributeValue Created
-------------------------------------------------------
1 'EmailPreference' 'Text' 1/10/2010
2 'EmailPreference' 'Html' 1/8/2010
如何使用SQL Server 2005做到这一点?
How can I do this using SQL Server 2005?
推荐答案
一种方法
select t1.* from (select ForeignKeyId,AttributeName, max(Created) AS MaxCreated
from YourTable
group by ForeignKeyId,AttributeName) t2
join YourTable t1 on t2.ForeignKeyId = t1.ForeignKeyId
and t2.AttributeName = t1.AttributeName
and t2.MaxCreated = t1.Created
另请参见包括汇总列的相关值，提供了5种不同的查询方式
See also Including an Aggregated Column's Related Values for 5 different ways to do this kind of query
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