Aggregate Function on Uniqueidentifier (GUID)
Solution 1
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
Solution 2
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
Solution 3
Aggregate functions can be used on Uniqueidentifier columns if SQL Server Version >= 2012
expression
Is a constant, column name, or function, and any combination of arithmetic, bitwise, and string operators. MIN can be used with numeric, char, varchar, uniqueidentifier, or datetime columns, but not with bit columns. Aggregate functions and subqueries are not permitted.
Solution 4
declare @T table(category char(1), guid uniqueidentifier)
insert into @T
select 'a', newid() union all
select 'a', newid() union all
select 'b', newid()
select
S.category,
S.guid
from
(
select
T.category,
T.guid,
row_number() over(partition by T.category order by (select 1)) as rn
from @T as T
) as S
where S.rn = 1
If you are on SQL Server 2000 you could to this
select
T1.category,
(select top 1 T2.guid
from @T as T2
where T1.category = T2.category) as guid
from @T as T1
group by T1.category
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Can Sahin
Updated on March 04, 2020Comments
-
Can Sahin about 4 years
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?
-
verdesmarald almost 13 yearsWhy are you doing this? Can you just use
SELECT DISTINCT category FROM myTable
instead? Or do you really need an arbitrary GUID for each category? -
Can Sahin almost 13 years@veredesmarald: Yes, I need an arbitrary GUID for each category.
-
-
J Webb almost 11 yearsyou could convert it to a string -
MIN(CAST(guid AS VARCHAR(36)))
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StuartLC about 10 years
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Can Sahin over 9 yearsThanks for the effort, but your answer is incorrect: TOP 1 will return only 1 record after grouping (i.e., the answer will contain only either
A
orB
).