Date: Fri, 1 May 2009 15:38:14 -0400
Reply-To: Michael Raithel <michaelraithel@WESTAT.COM>
Sender: "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From: Michael Raithel <michaelraithel@WESTAT.COM>
Subject: Re: basic questions about index a large SAS file
In-Reply-To: <b7a7fa630905011059s3a8c2c16td0d7522fe8bbc837@mail.gmail.com>
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Dear SAS-L-ers,
Omnipotent SAS-L Rookie of the Year Joe Matise posted the following regarding my reply to Christine:
>
> Michael, I think there might be a level of misunderstanding
> here... I think Christine is asking whether PROC MEANS
> (/SUMMARY) uses the index when you use the CLASS statement,
> not a WHERE statement. (I don't know the answer to that
> question myself unfortunately...) Unless I missed the answer
> to that in your answer somewhere?
>
Joe,
Thanks! As I mentioned in our brief, non-L side-bar conversation:
A second reading of the original post in light of your comments makes me think that you are right. The answer would be a categorical NO if that is what she is asking. SAS only drops the hammer on an index in four circumstances:
1. WHERE expression
2. BY statement
3. The KEY option on a MODIFY statement
4. The KEY option on a SET statement
It doesn't fire off an index just because an index key variable is a co-defendant in a CLASS statement.
Joe, best of luck in all of your SAS endeavors!
I hope that this suggestion proves helpful now, and in the future!
Of course, all of these opinions and insights are my own, and do not reflect those of my organization or my associates. All SAS code and/or methodologies specified in this posting are for illustrative purposes only and no warranty is stated or implied as to their accuracy or applicability. People deciding to use information in this posting do so at their own risk.
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Michael A. Raithel
"The man who wrote the book on performance"
E-mail: MichaelRaithel@westat.com
Author: Tuning SAS Applications in the MVS Environment
Author: Tuning SAS Applications in the OS/390 and z/OS Environments, Second Edition
http://www.sas.com/apps/pubscat/bookdetails.jsp?catid=1&pc=58172
Author: The Complete Guide to SAS Indexes
http://www.sas.com/apps/pubscat/bookdetails.jsp?catid=1&pc=60409
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Live so that you wouldn't be ashamed to sell the family parrot
to the town gossip. - Will Rogers
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