Re: index only table for single unique field?

If you are basically thinking about a single column table with a Unique index on that single column then it is almost certain that you should implement the table as an IOT, since

1. The space used will be ca. half that of an indexed heap table
2. The heap table would not be touch by most queries anyway

An IOT would be particularly useful in 8.1 for this, as the inevitable efficiency degradation of an index (assuming random insertions of new card numbers) can be eliminated by doing an ONLINE rebuild of the table. I have to say that I haven't yet done any tests of the performance overheads involved in doing such a rebuild on a large IOT though.

--

Jonathan Lewis
Yet another Oracle-related web site: http://www.jlcomp.demon.co.uk

tedchyn_at_yahoo.com wrote in message <7r3m07$u19$1_at_nnrp1.deja.com>...
>Sir, what is pro and cons for index only table in terms of performance ?
>I have a master credit card number which is unique by itself. Two
>alternatives are here:
>1. regular table with card_number field and unique index on card number
>and
>2. index only table with card)number field.
Received on Tue Sep 07 1999 - 14:28:35 CDT