[AccessD] Pass, Fail or Null

John Colby jwcolby at ColbyConsulting.com
Mon Oct 17 12:20:19 CDT 2005


Hmmm...

Assuming 

Pass is true (-1)
Fail is false (0)
And null is null

If you multiplied all the results, true/false and null...

Any null would cause a null for the whole result set
At the point where there are no more nulls, any fail would cause a fail (0
times anything = 0)
All passes would cause a true (either a -1 or a +1, depending on the number
of tests)

I know that MATH operations cause the null to win.

Logical AND also causes the Null to win

1 AND 1 AND 1 = 1 ( or TRUE AND TRUE AND TRUE)
1 AND 1 AND 0 = 0
1 AND 1 AND Null = Null

If you don't care that you have to wait for the entire set to be graded
before a FAIL can be seen, then this kind of thing works.  If you need to
know that a FAIL occurred even when there are still Nulls out there you will
need to do more processing.

John W. Colby
www.ColbyConsulting.com 

Contribute your unused CPU cycles to a good cause:
http://folding.stanford.edu/

-----Original Message-----
From: accessd-bounces at databaseadvisors.com
[mailto:accessd-bounces at databaseadvisors.com] On Behalf Of Nicholson, Karen
Sent: Monday, October 17, 2005 12:55 PM
To: Access Developers discussion and problem solving
Subject: [AccessD] Pass, Fail or Null


I have a subform that can have an infinite number of records.  On each line
is a result of that record.  If the test has not been performed, the result
is null.  If it has been performed, it can either be a pass or fail.  If the
record has 20 passes and one fail, then the entire record is a fail.
However, the tests instances are entered in, awaiting the test to be run, so
the test result is null until the values are filled in.  I am trying to pull
an overall result in the main form.  If all test results are null, or some
are null and some are pass, then the main form value would be null until all
tests are run.  My brain is not wrapping around this one - the nulls are
throwing me.  Ideas?

Karen S. Nicholson
Programmer Analyst
EG&G Technical Services, Inc.
Pittsburgh, PA
Phone: 412-386-6649
Email: cyx5 at cdc.gov


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