Date: Wed, 30 Jun 2004 16:47:53 -0400
Sender: "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From: "Paul M. Dorfman" <sashole@BELLSOUTH.NET>
Organization: Sashole of Florida
Subject: Re: Why would you ever merge without a by variable
Content-Type: text/plain; charset="us-ascii"
1. First (or rather last, but take it first), check your system option
MERGENOBY= supplied by SAS (in response to compaints similar to yours). It
is apparently currently set to NOWARN. Otherwise you can set it to WARN or
ERROR, which ought to be self-explanatory.
2. Second, Ian Whitlock has five golden rules (and presented them at the
most recent SESUG) which, if they are abided by, make MERGE virtually
bulletproof. "Never MERGE without BY" is one of the rules. I objected to
this point when Ian was first giving the talk a trial shot at Westat and
reminded him that one of the most useful ways to create a "lead" variable
looking N records ahead - introduced by Ian himself! - is
merge dataset dataset (firstobs = <N> rename = (var = _compvar)) ;
Well, Ian replied, create a unique key (for example, enumerate revords) and
merge by the key. Which is of course correct, but perhaps not very
efficient, so this is the single Ian's merge rule, to which I take
exception. However, since I do remember that there is a potential caveat, I
Paul M. Dorfman
> -----Original Message-----
> From: SAS(r) Discussion [mailto:SAS-L@LISTSERV.UGA.EDU] On
> Behalf Of Wainwright, Andrea
> Sent: Wednesday, June 30, 2004 4:17 PM
> To: SAS-L@LISTSERV.UGA.EDU
> Subject: Why would you ever merge without a by variable
> OK, I have spent the last couple of days chasing my tail
> trying to figure out my weird results, and of course it ended
> up being something stupid.
> I was merging, and I forgot to tell it BY my sorted variable.
> Would there ever be a reason to merge by not use a BY
> variable? Why isn't there at least a WARNING: that says "Hey
> idiot. You didn't use a BY variable."
> That would have saved me some time. (I am anal and do check the log.)
> Anyway, I am really just ranting, but I really would love a
> real world example where you merge without a BY variable.
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