IOT seek vs index seek - index sizes and widths.

If I only want to select 2 columns out of 5 for example, and those 2 columns are the primary key on an IOT, is it possible or even worthwhile to index them separately from the IOT? The IOT would be a much wider index and therefore require more memory? If the 2 columns are likely to be in physical order anyway, wouldn't the normal index perform better?

In SQL Server I have been able to create a clustered index and a normal index on the same 2 columns. The optimiser chooses the normal index when selecting just those 2 columns. But it seems Oracle won't let me define the same 2 columns(in the same order) twice.

Phil Received on Tue Apr 24 2007 - 03:52:10 CDT