[Year 12 IT Apps] Normal forms

Tue Oct 18 14:53:52 EST 2011

Thank you, thank you, thank you J 

That is so much easier and clearer. I think my kids have an actual
chance at understanding it now.

Laura

From: itapps-bounces at edulists.com.au
[mailto:itapps-bounces at edulists.com.au] On Behalf Of Brendyn Hancock
Sent: Tuesday, 18 October 2011 1:23 PM
To: Year 12 IT Applications Teachers' Mailing List
Subject: Re: [Year 12 IT Apps] Normal forms

Brilliant! Just Brilliant.

Thank you gents.

Brendyn

From: itapps-bounces at edulists.com.au
[mailto:itapps-bounces at edulists.com.au] On Behalf Of Mark KELLY
Sent: Tuesday, 18 October 2011 10:48 AM
To: Year 12 IT Applications Teachers' Mailing List
Subject: Re: [Year 12 IT Apps] Normal forms

Many thanks for the document, Robert. I've been looking for a while to
find a neat example of 1NF to 3NF progress.

I've taken the liberty of adapting it into a slideshow...

http://www.vceit.com/slideshows/database-normalisation-example.ppt

Cheers
Mark

On 17 October 2011 17:13, Timmer-Arends <timmer at melbpc.org.au> wrote:

Hello all

just to chip in my 2-cents worth, yes, there might be different
processes that lead to a normalised db, but the definitions of 1NF, 2NF,
and 3NF are pretty solid and have been for at least 30 years.

attached is my version of the story

Regards

Robert T-A

	----- Original Message ----- 

	From: Mark Scott <mailto:msc at luther.vic.edu.au>  

	To: Year 12 IT Applications Teachers' Mailing List
<mailto:itapps at edulists.com.au>  

	Sent: Monday, October 17, 2011 1:54 PM

	Subject: Re: [Year 12 IT Apps] Normal forms

	Joseph

	Your explanation looks and sounds simple enough but...

	There are at least half a dozen different definitions of this
process. (although the 1NF explanation is fairly consistent) 

	And, most importantly, we still do not know how the VCAA (Hi
Paula) defines the process of Normalisation and in particular the first
three forms.

	I'm expecting a very simple question on this on the exam
(hopefully just a 1NF question).

	Anything too complicated and this mailing list will be on fire
after the exam.

	thanks

	Mark Scott

	Luther College

	"Don't water the rocks" Gerry Smith, River Oaks Public School

	From: itapps-bounces at edulists.com.au
[mailto:itapps-bounces at edulists.com.au] On Behalf Of Joseph Papaleo
	Sent: Monday, 17 October 2011 1:36 PM
	To: Year 12 IT Applications Teachers' Mailing List
	Subject: Re: [Year 12 IT Apps] Normal forms

	Mark,
	In a nutshell, I've taught it as :

	1NF - tidy the table(s) up horizontally
	ie Fields contain only a single value eg Name: Mr Barney Rubble
changes to 
	Title: Mr
	Fname: Barney 
	Sname: Rubble

	Remove repeating Groups (as per Mark's comments)

	2NF - Tidy the table(s) up Vertically
	Eliminate duplication in records down the table by using a
Primary Key that each record refers to.
	Continue to do this as often as required until duplication is
removed from all tables- students should see the need for a new table if
there is duplication with their own unique Primary Key.

	3NF - Make all fields in a table Mutually Exclusive
	ie, no field can rely on another.  eg table may contain
"Quantity" and "Price", but it cannot contain "Total Cost" as Total cost
= Quantity x Price.

	I'm concerned that my students understand this, but they found
it difficult to do. Also concerned that I may have used an old or
inferior resource.

	Joseph Papaleo
	Ivanhoe Grammar School,
	Plenty Campus

	On Mon, Oct 17, 2011 at 1:04 PM, Mark KELLY
<kel at mckinnonsc.vic.edu.au> wrote:

	Groan.  I just spent another 30 minutes trying to explain the
differences between 2NF and 3NF to my dears.  
	As usual, by the time I finished, I think they knew less than
when I started.

	1NF is pretty clear cut...
	  - no duplicate rows (i.e. identical records)
	  - no multiple columns that contain the same *type* of data
(e.g. child1, child2, child3)
	  - only one piece of data per field (e.g. don't store 2 phone
numbers for a person in the 'phone' field; put street
address/suburb/postcode in separate fields; in Filemaker, don't use
repeating fields)  

	But 2NF is really only a problem if you use *multiple* fields as
a key (e.g.. using firstname + lastname + phone as a unique key) instead
of using a unique and arbitrary key field, like an ID number.  
	I realise now that my kids have trouble absorbing 2NF because at
no time in their database education have I ever *mentioned* the
possibility of using multiple fields as the key. So explaining 2NF to
them was a bit like warning them not to walk using their ears - the
concept had never even dawned on them before. To them, having a non-key
field that did not give information about *all* of the key fields was a
strange and scary possibility.

	3NF is, I think, relatively straight forward. Each non-key field
must give information about the key and not to another non-key field.
Violation of 3NF is usually pretty obvious because it looks "strange".

	After 2 slideshows, I'm still trying to work out a way to make
it sound really clear...  next time, maybe. If anyone has hit on a
sure-fire summary of differentiating normal forms, I'd love to hear of
it.

	Regards

	-- 
	Mark Kelly
	Manager of ICT, Reporting, IT Learning Area
	McKinnon Secondary College
	McKinnon Rd McKinnon 3204, Victoria, Australia
	Direct line / Voicemail: +613 8520 9085
<tel:%2B613%208520%209085> , Fax +613 9578 9253
<tel:%2B613%209578%209253> 
	kel at mckinnonsc.vic.edu.au
	VCE IT Lecture Notes: http://vceit.com
	Moderator: IT Applications Edulist <http://www.edulists.com.au/>

	Want a good time? Call 0112358. Ask for Mr Fibonacci.

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_______________________________________________
http://www.edulists.com.au - FAQ, resources, subscribe, unsubscribe
IT Applications Mailing List kindly supported by
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-- 
Mark Kelly
Manager of ICT, Reporting, IT Learning Area
McKinnon Secondary College
McKinnon Rd McKinnon 3204, Victoria, Australia
Direct line / Voicemail: +613 8520 9085, Fax +613 9578 9253
kel at mckinnonsc.vic.edu.au
VCE IT Lecture Notes: http://vceit.com
Moderator: IT Applications Edulist <http://www.edulists.com.au/> 

Want a good time? Call 0112358. Ask for Mr Fibonacci.

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