This is really Sharon Dooley. I have had trouble converting my customer ID to a SQL mag userid. I support what Brian has written. I have some apalling examples where scalar UDFs that do data base access generate thousands of IOs. You will see these in Profiler, but you will not see them with STATISTICS IO and you will not see them in the query plan. Intuitively, one expects UDFs to behave like stored procedures with cached plans and costing. However, this is not the case. In fact, the only functions for which plans are developed and costed are in-line table-valued functions. In SQL
Server 2005 the references to a UDF will show up in the query plan but they will not be costed (per Microsoft). I believe that the only "safe" function (from a performance point of view) is an in-line table-valued function.



Anonymous User 10/28/2004 7:52:12 PM