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Don't know if this will help: <br><br>
I'm not even a teacher let alone an IPM teacher - but I have fiddled with
databases in my chequered past and remember something about 3rd normal
form from the Grad Dip Comp course 20 odd years ago. I set up a quick
sample in Access to show how I would go about a student
database:<br><br>
<img src="cid:.0" width=489 height=190 alt="Emacs!"><br><br>
I would say that students and form have a 1 to 1 relationship, and that
students and stud_subj has a 1 to many relationship, but I'm only
guessing. <br><br>
rgds<br>
Jim<br><br>
<br><br>
At 05:25 PM 24/07/2008, you wrote:<br>
<blockquote type=cite class=cite cite="">Yes it is confusing but I would
still argue that it is one entity and that entity has a number of data
relationships in it. There is also only one Medicare card number on it
and that is unique – each child does not get their own Medicare card with
a different Medicare number. <br>
<br>
<br>
<br>
<br>
Kind regards<br>
<br>
Allan Barnes, CEO<br>
Australian Institute of Education and Training<br>
P.O. Box 171<br>
Brunswick West 3055<br>
Ph: (03) 9387 2051<br>
FAX: (03) 9387 3470<br>
Mobile: 0409 428 221<br>
<br>
<br>
<b>From:</b> itapps-bounces@edulists.com.au
[<a href="mailto:itapps-bounces@edulists.com.au" eudora="autourl">
mailto:itapps-bounces@edulists.com.au</a>] <b>On Behalf Of </b>Russo,
Frank R<br>
<b>Sent:</b> Thursday, 24 July 2008 8:33 AM<br>
<b>To:</b> Year 12 IT Applications Teachers' Mailing List<br>
<b>Subject:</b> RE: [Year 12 IT Apps] Database relationships<br>
<br>
Sorry but a medicare card can have multiple members in it but each member
can have their own card !!!<br>
<br>
Now that’s confusing………..<br>
<br>
Frank Russo<br>
ICT ~ Teaching & Learning<br>
Monterey Secondary College<br>
<hr>
<div align="center"></div>
<b>From:</b> itapps-bounces@edulists.com.au
[<a href="mailto:itapps-bounces@edulists.com.au" eudora="autourl">
mailto:itapps-bounces@edulists.com.au</a>] <b>On Behalf Of </b>Allan
Barnes<br>
<b>Sent:</b> Wednesday, 23 July 2008 9:14 PM<br>
<b>To:</b> 'Year 12 IT Applications Teachers' Mailing List'<br>
<b>Subject:</b> RE: [Year 12 IT Apps] Database relationships<br>
<br>
An example of a one-to-one relationship would be something like a
‘person’ entity and a ‘medicare card’ entity – one person can only have
one medicare card, and one medicare card can only belong to one
person.<br>
<br>
<br>
<br>
<br>
<br>
Kind regards<br>
<br>
Allan Barnes, CEO<br>
Australian Institute of Education and Training<br>
P.O. Box 171<br>
Brunswick West 3055<br>
Ph: (03) 9387 2051<br>
FAX: (03) 9387 3470<br>
Mobile: 0409 428 221<br>
<b>From:</b> itapps-bounces@edulists.com.au
[<a href="mailto:itapps-bounces@edulists.com.au" eudora="autourl">
mailto:itapps-bounces@edulists.com.au</a>] <b>On Behalf Of </b>Mia
Alexiou<br>
<b>Sent:</b> Wednesday, 23 July 2008 9:05 PM<br>
<b>To:</b> Year 12 IT Applications Teachers' Mailing List<br>
<b>Subject:</b> Re: [Year 12 IT Apps] Database relationships<br>
<br>
Hi all,<br><br>
I'm an intruder here (I tech year 11 not year 12) but I thought I could
share my somewhat rusty knowledge of databases.<br><br>
In response to Lisa's question the employee/department relationship is
one-to-many. As for "true" one-to-one relationships
I've never seen one in action and so doubt they are common at a small
database level. That being said, I can think of a couple of
situations where they might be useful such as splitting commonly needed
data from that which is rarely needed, to reduce the time it takes to run
queries over a huge table. Another reason might be security, with
highly sensitive data being stored in a separate table.<br><br>
A 0 or 1 to-many relationship is much more common and is what most people
(even in industry) usually mean when they talk about one-to-one
relationships. These are explained nicely (under the one-to-one
heading!) at
<a href="http://www.onlamp.com/pub/a/onlamp/2001/03/20/aboutSQL.html">
http://www.onlamp.com/pub/a/onlamp/2001/03/20/aboutSQL.html</a>.<br><br>
I hope this was helpful<br><br>
Mia Alexiou<br>
RMIT TAFE<br>
Information Technology<br>
Sessional Teacher<br>
On Wed, Jul 23, 2008 at 6:10 PM, Lisa Imms
<<a href="mailto:lisimms@copticvic.org">lisimms@copticvic.org</a>>
wrote:<br>
Hi Mark,<br><br>
Firstly, thanks for the resource :-)<br><br>
I hate to even contemplate disagreeing with you as my ITA class and I
regard you as the ITA font-of-all-knowledge, but I will try this
anyway.....<br><br>
Your example for one-to-one: "E.g. an employee's department data in
one table matches a corresponding department in another table, allowing
data relating to that department to be fetched."<br><br>
Wouldn't this be a one to many relationship? Even the line you have
joining them has the 'many feathers' at the employees table? Although
each employee can belong to only one department, each department can (and
will) have multiple employees? So it is actually a one to many
relationship?<br><br>
Am I correct in assuming that a well organised database would not have
any one-to-one relationships? The two tables in a one-to-one relationship
could/should just be merged into one table?<br><br>
Lisa Bairstow<br>
St Mary's Coptic Orthodox College<br><br>
________________________________<br><br>
From:
<a href="mailto:itapps-bounces@edulists.com.au">
itapps-bounces@edulists.com.au</a> on behalf of Mark Kelly<br>
Sent: Wed 7/23/2008 2:24 PM<br>
To: Year 12 IT Applications Teachers' Mailing List<br>
Subject: [Year 12 IT Apps] Database relationships<br><br>
<br><br>
Hi all. It's been mighty quiet here for a while. To perk
things up,<br>
here's a little revision for database relationships (1-1, 1-many,<br>
many-many) that may or may not be useful.<br><br>
Cheers<br>
Mark<br><br>
--<br>
Mark Kelly<br>
Manager - Information Systems<br>
McKinnon Secondary College<br>
McKinnon Rd McKinnon 3204, Victoria, Australia<br>
Direct line / Voicemail: 8520 9085<br>
School Phone +613 8520 9000<br>
School Fax +613 95789253<br>
kel AT
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IT Lecture notes: <a href="http://vceit.com">http://vceit.com</a>
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