Actually, for a little while (in SQL 2000) we used to pin tables in memory using the "dbcc pintable" command. It didn't load the entire table into memory by default, but once pages were read from disk, they would be cached in memory until you "unpinned" the table or restarted the server. This was pretty close to an in-memory database... for those tables which you pinned. However, this feature was deprecated in SQL 2005, mostly because the SQL engine does this kind of in-memory caching of pages automatically, as long as there is enough RAM (or so I have read). I was kind of sad to see it go though, because it did give a little bit of extra control and possibility for using all that RAM that servers have these days.

Jon