Date:         Wed, 21 Apr 1999 14:03:41 -0700
Reply-To:     "William W. Viergever" <wwvierg@IBM.NET>
Sender:       "SAS(r) Discussion" <SAS-L@UGA.CC.UGA.EDU>
From:         "William W. Viergever" <wwvierg@IBM.NET>
Subject:      Re: The WHERE statement does not work for rawdata
Comments: To: "Lambert, Bob" <Bob_Lambert@AFCC.COM>
In-Reply-To:  <851200E65752D211BC89006008CE5353777091@Z9999021.core.afcc. com>
Content-Type: text/plain; charset="us-ascii"

Wow; some heady stuff in this post-SUGI week!
 
FWIW, here's my $0.02:
 
The PDV is a "memory" constuct, as Paul thought, because it's nothing more than the output data buffer. When a data set is read, the descriptor provides the gamut of available vars -along with their length's and attributes, etc., and, after looking for DROPs, KEEPs, and other attribute changing statements (e.g., a LENGTH before the SET or MERGE stmt) it creates the PDV.
 
It was my understanding, also, that the WHERE clause is more efficient than subsetting IFs b/c it doesn't fill the entire PDV to evaluate the condition; i.e., a WHERE clause *does* work like a conditional INPUT stmt (i.e., trailing @ after reading in the evaluation var) would on raw, non-SAS, data step.
 
Where's Rick Langston or Pual Kent when you need 'em?
 
P.S. Is it "Debunkfication" or "Debunk-I-fication"?
 
 
 
At 01:01 PM 4/21/99 -0500, Lambert, Bob wrote:
>I believe the WHERE statement processes conditions BEFORE the PDV is loaded
>and is therefore more efficient than the IF statement.  I would appreciate
>further clarification or debunkfication on this.
>
>Thanx,
>
>Bob Lambert
>> -----Original Message-----
>> From: Adolf Quast [SMTP:adolf-a.quast@DB.COM]
>> Sent: Wednesday, April 21, 1999 7:25 AM
>> Subject:      Re: The WHERE statement does not work for rawdata
>>
>> Hi,
>>
>> the WHERE statement is very efficient because it uses the information
>> stored in
>> the PDV (program data vector) of a SAS-dataset. The PDV is created when a
>> SAS-Dataset is built. The PDV contains information about field length and
>> type.
>> Your rawdata do not have a PDV, so they have to be read via INFILE and
>> INPUT.
>>
>> Greetings
>>      Adolf Quast
 
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