Aggregate Function on Uniqueidentifier (GUID)

Question

Let's say I have the following table:

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

Basically, I want to do the following SQL:

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

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.

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?

Answer 1

Just cast it as a BINARY(16).

SELECT category, MIN(CAST(guid AS BINARY(16))) FROM myTable GROUP BY category 

You can cast it back later if necessary.

WITH CategoryValue AS (         SELECT category, MIN(CAST(guid AS BINARY(16)))     FROM myTable     GROUP BY category ) SELECT category, CAST(guid AS UNIQUEIDENTIFIER) FROM CategoryValue