Hi Niklas,
It's not a book. It is a PDF document, which you can download at:
http://www.eade.com/AccessSIG/downloads.htm
See the last download titled Understanding Normalization by Michael Hernandez, November 2002
(zipped PDF file 487 kb)
The paragraph I quoted is shown at the bottom of page 22 of this document.
Also, there are other papers available for download on the topic of normalization. Here are some
of them:
A shortened version from Mike Hernandez (4 pages):
http://www.datatexcg.com/Downloads/DatabaseDesignTips1997.pdf
And two links for Microsoft's KB site
http://support.microsoft.com/?id=234208
http://support.microsoft.com/?id=289533
Tom
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Thank´s Tom for clearing things up. I allways learn somthing new every day!
I´appreciate it!
In fact you wouldn´t hapen to have the ISBN number for this book?
// Niklas
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Karan,
As Niklas suggests, "...you don´t have to save the calculation, if you don't want to." In fact,
doing so is bad database design. Storing the results of a calculation violates third normal form
(3NF) for database design. Here is what Michael Hernandez, author of "Database Design for Mere
Mortals" has to say on this topic:
"The most important point for you to remember is that you will always re-introduce data integrity
problems when you de-Normalize your structures! This means that it becomes incumbent upon you or
the user to deal with this issue. Either way, it imposes an unnecessary burden upon the both of
you. De-Normalization is one issue that you'll have to weigh and decide for yourself whether the
perceived benefits are worth the extra effort it will take to maintain the database properly."
In other words, if you later changed the values in Fields 1, 2 or 3, you could have a data
integrity problem, unless you made absolutely sure that you recalculated the value that is stored
in Field 4.
Tom
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You can do it in a query or directly on a form on an unbound textbox.
In a query you could type following in an unbound field:
Sum: [Field1]+[Field2]+[Field3]
If you don´t want to create a query just for this you could type following
in row source of an unbound textbox on the form:
= [Field1]+[Field2]+[Field3]
Since you already have the data needed (Field1, Field2 and Field3) you
don´t have to save the calculation, if you don't want to. Which might be a
good idea if any of the values changes according to some other parameter (a
date for instance).
But if the data for each record in the three fields are stored and will not
change it´s enough if you calculate the result whenever you need it.
// Niklas
___________________________________________
"Karan" <
[email protected]> skrev i meddelandet
Hi,
I have three Field in a table having it's data type set as Number.
Now, i want to add these three Field Values and want that value to be put in an another Field.
Say for example:
Field 1> 12 Field 2> 8 Field 3> 2 want to add these values and Put in Field 4> 22
(After adding)
How can this be done? in Table or Query? pls, help me!!!
Karan
