Order by (select 0) meaning

Hi,

The thing I ask is probably very basic but I don't really get the point.

I found this query in one of the posts and I do not understand a part of it.

;WITH CTE AS
(
	SELECT	GroupID
	,		Name
	,		ROW_NUMBER() OVER(PARTITION BY GroupID ORDER BY (SELECT 0)) AS Ranking
	FROM	YourTable
)
SELECT	GroupID
,		Name
FROM	CTE
WHERE	Ranking = 1

I understand that ROW_NUMBER() requires an order by clause, but what order does 'order by (select 0)' generate? Why is it 0? Can it be any other constant?

Thanks.

P.