[Year 12 IT Apps] Normal forms

[Ben Hines]

I think the main problem we all find teaching the different normal forms, is that we teach students to create Databases well, so that they are already in at least 1NF.

So then teaching them that someone made a database (that is essentially an unusable mess) not in NF is too strange an idea to them.

Plus the databases we make in IT Apps are on the simpler side of Relational Databases. Understanding Normal Form took a fair while at Uni (and only by lots of practice designing databases), so I can understand why students find it difficult.

All the best with exam revision all!


[cid:image001.png at 01CC8CD4.B5FF61F0]
Mr Ben Hines

Maths/ICT Teacher
Senior School Campus - Christian College Geelong
*(03) 52411577 (ext. 212)



From: itapps-bounces at edulists.com.au [mailto:itapps-bounces at edulists.com.au] On Behalf Of Mark KELLY
Sent: Monday, 17 October 2011 1:04 PM
To: Year 12 IT Applications Teachers' Mailing List
Subject: [Year 12 IT Apps] Normal forms

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, Fax +613 9578 9253
kel at mckinnonsc.vic.edu.au<mailto:kel at mckinnonsc.vic.edu.au>
VCE IT Lecture Notes: http://vceit.com
Moderator: IT Applications Edulist<http://www.edulists.com.au/>

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