Re: how to update portion of the varchar type data

From: Paul Brewer <paul_at_paul.brewers.org.uk>
Date: Tue, 3 Dec 2002 21:52:20 -0000
Message-ID: <3ded2d8c_2@mk-nntp-1.news.uk.worldonline.com>

"damorgan" <damorgan_at_exesolutions.com> wrote in message news:3DECE157.4913D28B_at_exesolutions.com...
> Hkgirlygirl wrote:
>
> > if I index the column varchar(30) and
> > when I select my data by using order
> > by substr(item,4,3), will that do a table scan?
>
> Yes. The index will not be used.
>
> If you want an index on this portion of the explore using a function
> based index.
>
> Daniel Morgan
>

The point I was trying to make is that if a substring of the PK really has independent meaning (and may or may not need indexing separately), then we need to decompose the PK into separate attributes.

In this case, never mind function based indexes; revisit the design.

Regards,
Paul Received on Tue Dec 03 2002 - 15:52:20 CST