Date:         Wed, 2 Nov 2005 11:46:29 -0500
Reply-To:     "Michael S. Zdeb" <msz03@HEALTH.STATE.NY.US>
Sender:       "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From:         "Michael S. Zdeb" <msz03@HEALTH.STATE.NY.US>
Subject:      Re: What is the difference between NULL and MISSING in PROC SQL?
Comments: To: Glen Chen <ymmv_123@HOTMAIL.COM>
In-Reply-To:  <1130947687.171479.272280@z14g2000cwz.googlegroups.com>
Content-type: text/plain; charset=US-ASCII

Hi...this has been the subject of a bunch of notes on SAS-L in the past.
Check the archives at...

http://listserv.uga.edu/cgi-bin/wa?S1=sas-l

Also, there's a paper at SAS tech support...

http://support.sas.com/rnd/warehousing/papers/resultsets.pdf

that discusses NULL versus MISSING in relational databases and SAS, and a
NESUG paper...

http://www.nesug.org/html/Proceedings/nesug98/dbas/p004.pdf

that discusses missing values in PROC SQL.


Mike Zdeb
U@Albany School of Public Health
1 University Drive
Rensselaer, NY   12144-3456
(P)518-402-6479
(F)630-604-1475




             Glen Chen
             <ymmv_123@HOTMAIL
             .COM>                                                      To
             Sent by: "SAS(r)          SAS-L@LISTSERV.UGA.EDU
             Discussion"                                                cc
             <SAS-L@LISTSERV.U
             GA.EDU>                                               Subject
                                       What is the difference between NULL
                                       and MISSING in PROC SQL?
             11/02/2005 11:08
             AM


             Please respond to
                 Glen Chen
             <ymmv_123@HOTMAIL
                   .COM>






Hello, folks:

Could anybody kindly explain to me the difference b/w "NULL" and
"MISSING" when used in PROC SQL?

I didn't find any difference so far. Below is an example:
The only difference between the two PROC SQL blocks is NULL/MISSING. I
was given the same results from the two SQLs.

Any help is appreciated.
Glen

*================;

  data test;
   do value = "a","b","" ,"d"; output; end;
  run;

  proc sql;
  create table aaa as
  select *
  from test
  where value is not NULL;
  quit;

  proc sql;
  create table bbb as
  select *
  from test
  where value is not MISSING;
   quit;