[Year 12 IT Apps] Normalisation Activity

Thu May 1 17:19:50 EST 2014

Hello all

just be careful with this site though. Its definition of 1NF is not quite right and its 1NF example is wrong because of it.

In the following I am only referring to what appears under the heading 'First Normal Form 1NF'

'A row of data cannot contain a repeating group' - correct - note it's the row, not the column.
'Each column must have a unique value' - not correct. Think about it. In their example, this means you cannot have more than one student named 'Adam' or more than one appearance of the subject 'Maths'.
'Each row of data must have a unique identifier i.e primary key' - not quite. A primary key is the smallest number of columns that uniquely identify a row.
In fact, for their example, the inital Student table, which they say is not 1NF IS in 1NF, with a primary key = S_ID + Subject

The difficulty of course is that it uniquely identifies a student in a subject. Presumably the intention is for S_ID to be a primary key on its own, uniquely identifying a student.
In that case, the reason the table must be split has nothing to do with 1NF. The reason is that it is NOT in 2NF (assuming we want S_ID as the unique identifier). 2NF says that no column that is not part of a primary key can be dependent on only a part of the primary key. Clearly S_Name is dependent only on S_ID, not on S_ID + Subject.
So the split occurs as given, but leading to 2NF not 1NF (Yes, as they say, each of the split tables are in 1NF, but the two tables together are a 2NF representation of the initial Student table.

Regards
Robert T-A

----- Original Message ----- 
  From: Litsa Tzelepis 
  To: Year 12 IT Applications Teachers' Mailing List 
  Sent: Tuesday, April 29, 2014 2:59 PM
  Subject: Re: [Year 12 IT Apps] Normalisation Activity

  hi Sylvia - 

  would this help a little?

  litsa :-)

  http://www.studytonight.com/dbms/database-normalization.php

  On Tue, Apr 29, 2014 at 10:30 AM, Sylvia Pastore <smp191172 at gmail.com> wrote:

    Hi all 
    Would anyone have an access normalisation activity for my kids to try. Some of them are finding it a bit hard to grasp and thought someone may have created one to save me some time.

    Thanks in anticipation.
    sylvia

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