Date:         Wed, 10 Dec 2008 23:03:41 -0500
Reply-To:     "Howard Schreier <hs AT dc-sug DOT org>"
              <schreier.junk.mail@GMAIL.COM>
Sender:       "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From:         "Howard Schreier <hs AT dc-sug DOT org>"
              <schreier.junk.mail@GMAIL.COM>
Subject:      Re: Forcing Indexes and Preventing Index options
Content-Type: text/plain; charset=ISO-8859-1

On Tue, 9 Dec 2008 06:17:33 -0800, Irin later <irinfigvam@YAHOO.COM> wrote:

>Being new in SAS SQL Indexes, I got confused with understanding of� the
following options:
>�
>� When IDXWHERE = option is:
>Yes-SAS uses the best available index to process the WHERE
>������������� Expression, even if SAS estimates that sequential access is
>������������� Faster
>NO- SAS process the data sequentially even if SAS estimates that
>����������� Processing with an index is better��
>�
>I just wonder �.what might be hypothetical cases when both cases are
applicable?
>Could you please give me any example why it might be in need?
>�
>Thank you in advance,
>�
>Irin
>�

The critical word is "estimates". SAS may not always make the right
decision, so it's useful to be able to override.

I would look at Mike Raithel's book (http://tinyurl.com/5uxsuz).