Aggregate Function on Uniqueidentifier (GUID)

Question

Let\'s say I have the following table:

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

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