Try this:

[font="Courier New"]DECLARE @v-2 AS NVARCHAR(MAX)

SELECT TOP 10000 @v-2 = coalesce(@v + CAST(N', ' AS NVARCHAR(MAX)) + CAST(M1.Name AS NVARCHAR(MAX)), CAST(M1.Name AS NVARCHAR(MAX)) FROM master.Sys.Columns M1 CROSS JOIN master.Sys.Columns M2 ORDER BY M1.Name

PRINT DATALENGTH(@v)[/font]