Date:         Thu, 18 Aug 2005 16:06:47 -0700
Reply-To:     David L Cassell <davidlcassell@MSN.COM>
Sender:       "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From:         David L Cassell <davidlcassell@MSN.COM>
Subject:      Re: MODIFY with BY-groups?
In-Reply-To:  <MC5-F338qErQQB2IAGj0024fbec@mc5-f33.hotmail.com>
Content-Type: text/plain; format=flowed

I wrote:
> > But the MODIFY statement
> > seems totally inappropriate for your task.
> > then this is pretty straightforward as a SET statement with a BY
>statement

And Jens replied:
>A SET statement creates a complete new table!
>
>You can do that with 30 observations, not with 10 million and not if
>the table is not a SAS table but a MySQL table.

I think you'll *have* to create a new table, no matter what, even
if it supercedes the original.

You want to add a new variable to the data set.  That means you
cannot just use a MODIFY in a DATA step, and you cannot make
minor changes to your 10 million record database.  MySQL maintains
databases in fixed-length records for faster indexing and access.  It
will have to re-write the entire database no matter what.

And you want to eliminate a lot of rows, so the final database may
be *much* shorter than the original.  If you don't have the permissions
to create a new MySQL database, I think you'll have to talk with your
MySQL administrators either way.

David
--
David L. Cassell
mathematical statistician
Design Pathways
3115 NW Norwood Pl.
Corvallis OR 97330

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