[Year 12 IT Apps] Unit 3 2015
Poke, Michael C
poke.michael.c at edumail.vic.gov.au
Thu Nov 6 08:17:06 EST 2014
Hi all,
Thinking about our Year 11 to 12 orientation week coming up soon. Firstly, I'm thinking about getting U3O2 out of the way first while the students are fresh and motivated. Anyone else think this is a good idea?
Secondly, I'm still trying to decide on the most suitable RDMS for my Apple Mac school. I had plenty of headaches with both Libre Office and Open Office this year. Program crashes leading to last work were very demotivating for the students. Filemaker Pro seems like a very expensive option too.
Cheers,
Michael Poke
Manor Lakes P-12 College
On 5 Nov 2014 22:24, "itapps-request at edulists.com.au" <itapps-request at edulists.com.au> wrote:
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Today's Topics:
1. Re: First Normal Form (Robert Timmer-Arends)
2. HOLD THE DATE - BiG Day In @ RMIT - Thursday 28 May 2015
(Kerrie Bisaro)
----------------------------------------------------------------------
Message: 1
Date: Wed, 5 Nov 2014 18:13:45 +1100
From: "Robert Timmer-Arends" <timmer at westnet.com.au>
Subject: Re: [Year 12 IT Apps] First Normal Form
To: "Year 12 IT Applications Teachers' Mailing List"
<itapps at edulists.com.au>
Message-ID: <1F0AC1E4DEB34E919268198B478B58D8 at timmerarends>
Content-Type: text/plain; charset="utf-8"
Hello all
There is one extra component to 1NF that I feel needs to be stated explicitly.The table must have a primary key; that is, a column or group of columns which uniquely identify a given row. This is important because without reference to a primary key, 2NF and 3NF are not possible.
And the definition about 'there may only be one datum' is correct as far it goes, but "16 Fred Street Melbourne 3000" can be a single datum. It depends on the design needs of the db.
It many ways I find it best to incorporate some of OO terminology - a column is equilvalent to a class, and any individual field in the column can only contain one instance of that class.
So, for example, if the column were "address" and address was defined as "street address + suburb + post code" then "16 Fred Street Melbourne 3000" is one datum (one instance of the class 'address').
Whether 'address' is further split or not has to do with search requirements, not normalisation.
So
name phone
fred smith 345678000
543265465
suzy lang 101010101
(primary key = name) is NOT 1NF (repeated phone number, or two instances of phone number in the same row)
and
name phone1 phone2
fred smith 345678000 543265465
suzy lang 101010101
(primary key = name) is NOT 1NF (different column names, but still two instances of the same class of data)
but
name phone
fred smith 345678000
fred smith 543265465
suzy lang 101010101
(primary key = name+phone) IS 1NF (no repeating groups, but the primary key has to be extended. In a 'real db, because there could be many fred smiths and suzy langs, we would have a single ID field as a primary key, and because we most probably want to search on family name, we would probably split the name field)
Regards
Robert T-A
----- Original Message -----
From: Mark
To: Year 12 IT Applications Teachers' Mailing List
Sent: Wednesday, November 05, 2014 9:39 AM
Subject: Re: [Year 12 IT Apps] First Normal Form
Hi Stephanie. Now you know why I bailed out when I did :-)
1NF is easy:
- there must be no repeated columns (fields) e.g. Contact person 1, Contact person 2, Contact person 3.
- there may only be one datum in any field - i.e. no "16kg" "3 minutes 56 seconds", "Large Size $4, Small $2.50", "16 Fred St, Melbourne, 3000".
2NF problems ONLY arise if you're silly enough to use a multi-field key (e.g. using firstname & familyname to uniquely identify people in a table).
2NF problems never even arise if each table has its own dedicated key field (e.g. ID, account number).
But anyway, kids are expected to know 2NF.
2NF requires:
- 1NF has already been achieved.
- Any non-key field in a table is dependent on ALL of the fields used as the primary key.
As usual, this means as little as American football, so an example is needed.
There's a table with the following fields. 1NF has already been achieved.
StudentID
SubjectID
Mark
SubjectName
e.g. (Hope the formatting is not mangled - wish I could insert a table)
STUDENTID SUBJECTID Mark SubjectName
SMI0001 ENG A+ English
SMI0001 MA B Maths
FRE0002 ENG C English
The table's key is STUDENTID and SUBJECTID (together) to uniquely identify each record in the table.
The (non-key) MARK field is dependent on both STUDENTID and SUBJECTID - i.e. to find out what a mark refers to, you need to know both the student and subject.
However, the (non-key) SUBJECTNAME field is dependent only the SUBJECTID - i.e. to find out what a subject name refers to, you only need the SUBJECTID. You don't need the STUDENTID.
So the (non-key) SUBJECTNAME field is dependent on part of the key (SUBJECTID) but not the whole key (STUDENTID+SUBJECTID).
So it fails 2NF.
To fix the problem, the table must be broken into two -
- MARKS_TABLE with STUDENTID+SUBJECTID as its key. It also contains the MARK non-key field.
- SUBJECTS_TABLE with SUBJECTID (primary key) and non-key SUBJECTNAME.
You then create a relationship between the MARKS table and the SUBJECTS table using their primary keys as the related fields.
Now, in the MARKS table, a Mark is dependent upon the entire key in its table (STUDENTID+SUBJECTID).
In the SUBJECTS table, a subject name is dependent on the entire key in its table (SUBJECTID).
Bingo. 2NF.
Hope that helps.
On 5 November 2014 08:53, Stephanie Polan <pos at mckinnonsc.vic.edu.au> wrote:
Good Morning everyone,
I know this is crazy... but my 12's are making me crazy, does anyone have any simple blunt help for Normal Form's ie 1NF 2NF. I've gone through my explanations and Mark Kelly's slide show and my patience and my students are still asking for clarification because of course they can learn and remember it for Friday!!!
Thanks in advance
Stephanie Polan
--
Miss Polan
McKinnon SC
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Message: 2
Date: Sun, 2 Nov 2014 21:36:55 +0000
From: Kerrie Bisaro <Kerrie.Bisaro at acsfoundation.com.au>
Subject: [Year 12 IT Apps] HOLD THE DATE - BiG Day In @ RMIT -
Thursday 28 May 2015
To: Kerrie Bisaro <Kerrie.Bisaro at acsfoundation.com.au>
Message-ID:
<2bde34b15cf4434b8f663f75b8c15516 at SINPR04MB187.apcprd04.prod.outlook.com>
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Attention Careers Advisers,
IT Teachers & all Year 9-12 students
interested in Technology
Save the Date!!
28 May 2015
BiG Day In(tm)
@ RMIT
[RMIT]
The ACS Foundation and RMIT University are delighted to invite you and your students along to the BiG Day In IT Careers Conference in Storey Hall, RMIT University on Thursday 28 May 2015.
Join us to hear leading speakers from companies such as Westpac and WiseTech Global plus loads more to come, talking about the future of technology and how students can get involved in shaping the future. Hear from cool industry speakers & visit exhibitor stands to learn about where a career in IT can take you - more speakers & exhibitors to be confirmed in early 2015 - don't miss out, book your seats early!!
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