Re: indexing a column with only 2 or 3 values

From: ciapecki <ciapecki_at_gmail.com>
Date: Fri, 03 Aug 2007 00:58:44 -0700
Message-ID: <1186127924.502727.241260@x40g2000prg.googlegroups.com>

On 3 Aug., 09:54, Thomas Kellerer <JUAXQOSZF..._at_spammotel.com> wrote:
> ciapecki wrote:
> > Hi,
>
> > Does indexing a very big table (about 5Mio records) on the columnA
> > which can hold only values Y,N,<NULL> make sense?
>
> Yes, that's what bitmap indexes were made for.
>
> Thomas

Thanks Thomas,

Is there any rule when to use BMap and when BTree? I know for a few values BMap, for many different ones BTree, but maybe there is some mathematical equation that helps to determine which Index is better.

chris Received on Fri Aug 03 2007 - 02:58:44 CDT