[AccessD] normalization question

John W. Colby jcolby at colbyconsulting.com
Thu Mar 13 16:57:00 CST 2003


Charles,

>It would be a very simple application, or a very astute individual, where
all the relationships are obvious from the beginning.

I would agree with that.

>By that I mean as you go along you will discover that one or more of the
tables you have already designed needs to be split since some of the data
fields apply only to the subject of the table while other data fields does
not.

This implies that you are not designing tables using the simple rule "is it
a property of the object this table models".

Each table models an object.  Banks, Account Holders, accounts, checks etc.
There is no reason to be putting account holder info in the account table or
vice versa.  Account Holders are people, Accounts are not.

The only case I can think of where you might put data in a table when it
belongs in another is in the case of a property that ends up plural.
Addresses are an example.  A company has an address.  Oops, it can have TWO
(or 10) addresses.  In this case, the data (addresses) ARE still properties
of the object (company) it's just that the company can have several of that
property (addresses) and thus they have to be a child table.

John W. Colby
Colby Consulting
www.ColbyConsulting.com

-----Original Message-----
From: accessd-admin at databaseadvisors.com
[mailto:accessd-admin at databaseadvisors.com]On Behalf Of Wortz, Charles
Sent: Monday, March 10, 2003 2:48 PM
To: accessd at databaseadvisors.com
Subject: RE: [AccessD] normalization question


Susan,

Whether you do it on paper or on the PC, it usually is an iterative
process, at least in my experience.  By that I mean as you go along you
will discover that one or more of the tables you have already designed
needs to be split since some of the data fields apply only to the
subject of the table while other data fields does not.  And you will
notice that some data fields split over several tables should be
combined into one table.

It would be a very simple application, or a very astute individual,
where all the relationships are obvious from the beginning.

Charles Wortz
Software Development Division
Texas Education Agency
1701 N. Congress Ave
Austin, TX 78701-1494
512-463-9493
CWortz at tea.state.tx.us



-----Original Message-----
From: Susan Harkins [mailto:harkins at iglou.com] 
Sent: Monday 2003 Mar 10 12:50
To: accessd at databaseadvisors.com
Subject: Re: [AccessD] normalization question

Yes, I agree...

but in the process of making your paper lists -- when?


----- Original Message -----
From: <Mwp.Reid at Queens-Belfast.AC.UK>
To: <accessd at databaseadvisors.com>
Sent: Monday, March 10, 2003 1:34 PM
Subject: RE: [AccessD] normalization question


>
> you do it before turning the PC on when your designing the structures.

> The theory is that the data is normalised before you actually create 
> the
tables
> physically.
>
> Martin
>
> (<:
>
>
>
> Quoting Charlotte Foust <cfoust at infostatsystems.com>:
>
> > I tend to do it at the time so I don't forget.  Of course, as we get

> > older our memory ... Uh, what was I saying?  <vbg>
> >
> > Charlotte Foust
> >
> > -----Original Message-----
> > From: Susan Harkins [mailto:harkins at iglou.com]
> > Sent: Sunday, March 09, 2003 3:36 PM
> > To: AccessD at databaseadvisors.com
> > Subject: [AccessD] normalization question
> >
> >
> > When you remove a field to another table (for whatever reason), do 
> > you immediately create the foreign key in the original table, or do 
> > you wait until you've completely normalized each table and then 
> > return to the tables and insert all the foreign keys then?
> >
> > I tend to do it later because the nature of a single field can 
> > change.
> >
> > Does anyone know if the relational model requires a particular 
> > routine?
> >
> > Just curious.
> >
> > Susan H.
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