I have seen the use of UDFs in the WHERE clause result in FIVE ORDERS OF MAGNITUDE WORSE PERFORMANCE. Run a statement level profiler trace (preferably to disk to avoid massive overhead). I can't count the number of clients I have had that went "holy SH-T" when they saw row-by-row processing of their spiffy SELECT statement... :w00t:
Best,
Kevin G. Boles
SQL Server Consultant
SQL MVP 2007-2012
TheSQLGuru on googles mail service