4 NF (Normal form)

4 NF (Normal form)

Post by Benedikt Wisma » Fri, 10 Feb 1995 23:40:30



Dear database experts,

we have a discussion here about the definition
of 4th normal form.

a) A Relation r of type R is in 4 NF, if it is in 3NF
   and all multivalued dependencies in fact are
   functional dependencies.

   for example Rob/Coronel, Database Systems ... (?)

b) the same defintion, except 3NF is substituted by BCNF

   for example Date, An Introduction ...

Any dicussion, literature, ... is welcome.

regards,

Benedikt Wismans
Universitaet Bamberg

 
 
 

1. 2nd Normal Form and Pdox Forms

Hi All:

I have a question about using database 2nd normalization and
displaying the results on Paradox forms.

The example of a 2nd Normal Form (2NF) that Mike Prestwood uses in his
Paradox 9 book is of telephone numbers.  Any given individual can have
many telephone numbers (I prefer to use the term "Comm Services") such
as telephone, fax, e-mail, beeper, cell phone, etc.  And some may have
only one or two. (In my business there are several other prime areas
for 2NF.) To avoid using up space and resources for those who have few
to make room for those who have many, the 2NF is recommended.  So the
individual would be referenced in the 2nd table by, say, LastName and
FirstName, and then the table would have a field for Device and a
Field for number.  So, in "device" you could put Phone, or cell, or
beeper or what-have-you and then the number (or e-mail address) in the
"number" field.

My question is how to display the info on a form since the Device
field will vary.  It could display Phone or Cell for example, so could
you have a fixed spot for Telephone and Cell?  Wouldn't the display
vary?  The only thing I could see was using a table frame to display
"Comm Services" and then just have whatever popped up displayed.  Is
this the only way to handle 2nd normal forms?  If so, I'm not very
satisfied with that solution.

Ken

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