[Informatics] Data normalisation

Tue Oct 4 22:43:58 AEDT 2016

As I've always said: if you create 2NF problems, you should not be in
charge of a database.
2NF problems only occur because of stupid design - using multiple existing
fields as a key.

It irks me when exams artificially labour 2NF scenarios. It seems like a
medical school exam asking students to explain how to treat the infection
caused by letting rabid chimpanzees into the operating room during an
operation.

The only correct answer is: don't be dumb enough to let the frothy chimps
in.

On Tuesday, 4 October 2016, Matheson, Heath A <
Matheson.Heath.A at edumail.vic.gov.au> wrote:

> Hi Gang,
>
> I went and had another look at Mark’s normalisation slideshows from his
> website, definitely not from my computer or Litsa’s e-mail. I still really
> struggle to explain the practical difference between 2NF and 3NF, I think
> because I see the purpose of doing 2NF and 3NF to be the same (data
> integrity).  I have no problems in normalising to third level. I find that
> easy. But I think if asked to turn 1NF to 2NF I would go straight to 3NF.
> This would be faster than trying to work out what I can leave to make it
> 2NF. So I need some help.
>
> From the example slideshow:
>
> But if you said “One reason this table is not 2NF is that House Colour is
> not dependent on Subject” would you be wrong? What makes you wait until
> later to deal with House Colour?
>
> Also, If you were asked to make (or describe how to make) a database 2NF
> and you made it 3NF could you be marked down? I would think not.
>
>
>
> Cheers,
>
> Heath Matheson
>
> Mount Soggy Secondary College
>
>
>
> *From:* informatics-bounces at edulists.com.au
> <javascript:_e(%7B%7D,'cvml','informatics-bounces at edulists.com.au');>
> [mailto:informatics-bounces at edulists.com.au
> <javascript:_e(%7B%7D,'cvml','informatics-bounces at edulists.com.au');>] *On
> Behalf Of *Mark
> *Sent:* Tuesday, 4 October 2016 8:48 PM
> *To:* Year 12 VCE Informatics Teachers' Mailing List
> *Subject:* Re: [Informatics] Data normalisation
>
>
>
> Hi Robert.  Thanks for the message.
>
>
>
> I have no worries about criticism of my materials.
>
>
>
> The status of message recalls has never come up before, so I thought it
> timely to establish a policy for the future.
>
>
>
> Regards
>
> Mark
>
> On Tuesday, 4 October 2016, Robert Hind <robert at yinnar.com
> <javascript:_e(%7B%7D,'cvml','robert at yinnar.com');>> wrote:
>
> Sorry Mark.
>
> And sorry that I ended up criticising one of your PowerPoint presentations
> which is freely available on your own vceit website.
>
>
>
> Robert Hind
>
> Ex Traralgon and Ashwood
>
> Retired
>
>
> ------------------------------
>
> *From:* informatics-bounces at edulists.com.au [mailto:informatics-bounces@
> edulists.com.au] *On Behalf Of *Mark
> *Sent:* Tuesday, 4 October 2016 7:25 PM
> *To:* Year 12 VCE Informatics Teachers' Mailing List
> *Subject:* Re: [Informatics] Data normalisation
>
> I would have thought that if the sender of a message said that the post
> was not intended for the list, recipients would delete it, and
> certainly not respond to its contents.
>
>
> On Tuesday, 4 October 2016, Robert Hind <robert at yinnar.com> wrote:
>
> Well Litsa you did send the ppt files to all of us and I was interested
> enough to have a look at the example file.
>
>
>
> Now I must take exception to slides 26 and 27 - pics below
>
>
>
> Both the statements on yellow background are false. The HouseColor depends
> only on the HouseName (or vice versa), not directly on the StudentID.
>
>
>
> As almost noted in slide 28 " These two non-key fields are more dependent
> on each other than they are on the primary key"
>
>
>
> The key 3NF rule here is: *"remove to a new table any non-key attributes
> that are more dependent on other non-key attributes than the table key"*
>
>
>
> So we move HouseName and HouseColor to a new table and leave just
> HouseName in the Student table.
>
>
>
> Robert Hind
>
> Ex Traralgon and Ashwood
>
> Retired
>
>
>
>
> ------------------------------
>
> *From:* informatics-bounces at edulists.com.au
> <javascript:_e(%7B%7D,'cvml','informatics-bounces at edulists.com.au');> [
> mailto:informatics-bounces at edulists.com.au
> <javascript:_e(%7B%7D,'cvml','informatics-bounces at edulists.com.au');>] *On
> Behalf Of *Litsa Tzelepis
> *Sent:* Tuesday, 4 October 2016 2:54 PM
> *To:* Year 12 VCE Informatics Teachers' Mailing List
> *Subject:* [Informatics] Data normalisation
>
>
>
>
> --
>
> Litsa Tzelepis
> Mount St. Joseph Girls' College
> 133 Maidstone Street, Altona, VIC. 3018
> htzelepis at msj.vic.edu.au
> <javascript:_e(%7B%7D,'cvml','htzelepis at msj.vic.edu.au');>
> P:8398 2000 | F:9398 3498
>
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> --
>
>
>
> Mark Kelly
>
>
>
> mark at vceit.com
>
> http://vceit.com
>
>
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>
> Mark Kelly
>
>
>
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-- 

Mark Kelly

mark at vceit.com
http://vceit.com
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