Hugo is 100% correct! Using this technique is 100% unpredictable. It will not work with table variables, derived tables, etc.

If you need to make a delimited list of values use XML.

Example:

The following code will create a semi-colon delimited list of user names where "NAME" contains names in the format of "LastName, FirstName".

SELECT STUFF(V.DELIMITED_LIST, 1, 2, N'')

FROM

(

SELECT

N'; ' + U.NAME AS "text()"

FROM

USERS U

WHERE U.NAME IS NOT NULL -- exclude any NULL values

AND U.NAME <> N'' -- exclude any zero-length strings

ORDER BY 1

FOR XML PATH(N'')

) AS V (DELIMITED_LIST)