I'm working with a client who had a SQL Server 2008 converted from a SQL Server 2000 DB and one of the queries has quite dramatically increased in time since it was on SQL Server 2000.
However, if I change the compatibility level to 2008 in the DB, the query goes like a rocket (40-50 times faster).
The query does use a number of UDFs.
My questions: - are there issues with running SQL2000 compatibility in SQL Server 2008 - has SQL Server 2008 improved the performance when using UDFs?