Thank you Robert. I completely didn't notice that. Thank you for clarifying and sorry if anyone has been confused by it. <div><br></div><div>Ta, litsa :-)<br><br>On Thursday, May 1, 2014, Robert Timmer-Arends <<a href="mailto:timmer@westnet.com.au">timmer@westnet.com.au</a>> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><u></u>
<div bgcolor="#ffffff">
<div><font face="Arial">Hello all</font></div>
<div><font face="Arial"></font> </div>
<div><font face="Arial">just be careful with this site though. Its
definition of 1NF is not quite right and its 1NF example is wrong because of
it.</font></div>
<div><font face="Arial"></font> </div>
<div><font face="Arial">In the following I am only referring to what
appears under the heading 'First Normal Form 1NF'</font></div>
<div><font face="Arial"></font> </div>
<div><font face="Arial">'A row of data cannot contain a repeating group' -
correct - note it's the row, not the column.</font></div>
<div><font face="Arial">'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'.</font></div>
<div><font face="Arial">'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.</font></div>
<div><font face="Arial">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</font></div>
<div><font face="Arial"></font> </div>
<div><font face="Arial">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.</font></div>
<div><font face="Arial">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.</font></div>
<div><font face="Arial">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.</font></div>
<div><font face="Arial"></font> </div>
<div><font face="Arial">Regards</font></div>
<div><font face="Arial">Robert T-A</font></div>
<div><font face="Arial"></font> </div>
<div>----- Original Message ----- </div>
<blockquote style="BORDER-LEFT:#000000 2px solid;PADDING-LEFT:5px;PADDING-RIGHT:0px;MARGIN-LEFT:5px;MARGIN-RIGHT:0px">
<div style="FONT:10pt arial;BACKGROUND:#e4e4e4"><b>From:</b>
<a title="htzelepis@msj.vic.edu.au" href="javascript:_e(%7B%7D,'cvml','htzelepis@msj.vic.edu.au');" target="_blank">Litsa
Tzelepis</a> </div>
<div style="FONT:10pt arial"><b>To:</b> <a title="itapps@edulists.com.au" href="javascript:_e(%7B%7D,'cvml','itapps@edulists.com.au');" target="_blank">Year 12 IT Applications Teachers' Mailing
List</a> </div>
<div style="FONT:10pt arial"><b>Sent:</b> Tuesday, April 29, 2014 2:59
PM</div>
<div style="FONT:10pt arial"><b>Subject:</b> Re: [Year 12 IT Apps]
Normalisation Activity</div>
<div><br></div>
<div dir="ltr">
<div style="FONT-FAMILY:arial,helvetica,sans-serif" class="gmail_default">hi
Sylvia - </div>
<div style="FONT-FAMILY:arial,helvetica,sans-serif" class="gmail_default"><br></div>
<div style="FONT-FAMILY:arial,helvetica,sans-serif" class="gmail_default">would
this help a little?</div>
<div style="FONT-FAMILY:arial,helvetica,sans-serif" class="gmail_default"><br></div>
<div style="FONT-FAMILY:arial,helvetica,sans-serif" class="gmail_default">litsa
:-)</div>
<div style="FONT-FAMILY:arial,helvetica,sans-serif" class="gmail_default"><br></div>
<div class="gmail_default"><font face="arial, helvetica, sans-serif"><a href="http://www.studytonight.com/dbms/database-normalization.php" target="_blank">http://www.studytonight.com/dbms/database-normalization.php</a></font><br>
</div>
<div class="gmail_default"><font face="arial, helvetica, sans-serif"><br></font></div></div>
<div class="gmail_extra"><br><br>
<div class="gmail_quote">On Tue, Apr 29, 2014 at 10:30 AM, Sylvia Pastore <span dir="ltr"><<a href="javascript:_e(%7B%7D,'cvml','smp191172@gmail.com');" target="_blank">smp191172@gmail.com</a>></span> wrote:<br>
<blockquote style="BORDER-LEFT:#ccc 1px solid;MARGIN:0px 0px 0px 0.8ex;PADDING-LEFT:1ex" class="gmail_quote">
<div dir="ltr">Hi all
<div>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.</div>
<div><br></div>
<div>Thanks in anticipation.</div><span><font color="#888888">
<div>sylvia</div></font></span></div><br>_______________________________________________<br><a href="http://www.edulists.com.au" target="_blank">http://www.edulists.com.au</a> - FAQ, resources, subscribe,
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<div><br></div>-- <br>
<div dir="ltr">
<div><font size="1">Litsa Tzelepis<br>Mount St. Joseph Girls' College<br>133
Maidstone Street, Altona, VIC. 3018<br></font><a href="javascript:_e(%7B%7D,'cvml','htzelepis@msj.vic.edu.au');" target="_blank"><font size="1">htzelepis@msj.vic.edu.au</font></a><br><font size="1">P:8398 2000 |
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