唯一标识符（GUID）上的汇总函数 [英] Aggregate Function on Uniqueidentifier (GUID)

问题描述

假设我有下表：

category | guid
---------+-----------------------
   A     | 5BC2...
   A     | 6A1C...
   B     | 92A2...

基本上，我想执行以下SQL：

Basically, I want to do the following SQL:

SELECT category, MIN(guid)
  FROM myTable
 GROUP BY category

不一定必须是MIN。我只想返回每个类别的一个 GUID。我不在乎哪一个。不幸的是，SQL Server不允许GUID上的MIN或MAX。

It doesn't necessarily have to be MIN. I just want to return one GUID of each category. I don't care which one. Unfortunately, SQL Server does not allow MIN or MAX on GUIDs.

当然，我可以将guid转换为varchar，或创建一些嵌套的TOP 1 SQL，但是似乎是一个丑陋的解决方法。我错过了一些优雅的解决方案吗？

Of course, I could convert the guid into a varchar, or create some nested TOP 1 SQL, but that seems like an ugly workaround. Is there some elegant solution that I've missed?

推荐答案

假定您使用的是SQL Server 2005或更高版本：

Assuming you're using SQL Server 2005 or later:

;with Numbered as (
     select category,guid,ROW_NUMBER() OVER (PARTITION BY category ORDER BY guid) rn
     from myTable
)
select * from Numbered where rn=1

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