SPLIT doesn't do that. Split breaks UPDATEs into a DELETE and INSERT.
You say # is the delimiter, but your example: 2 21 31 4 3 5
doesn't have any # symbols. So are the numbers separated by a space or by the #?
You could try REPLACE:
SELECT REPLACE(column_name, ' ', ',')
Refer to the BOL for more information on REPLACE.
-SQLBill
BOL=Books OnLine=Microsoft SQL Server's HELP
Installed as part of the Client Tools
Found at Start>Programs>Microsoft SQL Server>Books OnLine
Posting advice: FAQ481-4875