Тут же хочу обратить внимание на полезный пост из ранее прорекламировано блога.
Overview of updates for SQL Server 2005 SP2
3) Some queries ran faster on SQL2000 than they do on SQL2005
KB 942659 / SQL Hotfix bug number50001716:
FIX: The query performance is slower when you run the query in SQL Server 2005 than when you run the query in SQL Server 2000
This problem was experienced by a very few NAV customers after they upgraded from SQL2000 to SQL2005. The symptoms were: When changing a field filter (F7) on "Name" in a contact list, the response would take a couple of seconds. The same actions would give instant response on SQL2000. This problem did not cause drastic table scans, "only" 3-5.000 more reads than SQL 2000 would have done. But of course, in a multi user system this would cause a lot of unnecessary reads.
The correction was to implement a new trace flag 4119. Enabling this trace flag will set SQL2005's behaviour to that of SQL2000 for these specific queries. This trace flag is further documented in this post: New trace flag in Update 4 for SQL 2005 SP2
This correction is included in cumulative update 4.