Date:         Tue, 9 Jun 2009 09:56:11 +0800
Reply-To:     shao xiaolong <sxlion2@GMAIL.COM>
Sender:       "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From:         shao xiaolong <sxlion2@GMAIL.COM>
Subject:      Re: First and Last Observation
In-Reply-To:  <200906082336.n58NVfiK003158@malibu.cc.uga.edu>
Content-Type: text/plain; charset=ISO-8859-1

I don't think you can avoid the second sort.

the fellowing only reduce a data step,

proc sort  data =have ; by ID1 Date time ID2 ID3 ; run;
proc sort  data =have ; by ID1 Date  ID2 ID3 ; run;

data last ;
set have;
by ID1 date ID2 ID3 ;
 FO = first.ID3  ;
 LO = last.ID3 ;
run;