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Doubts on Normalisation [message #377151] Sat, 20 December 2008 14:38 Go to next message
Messages: 42
Registered: November 2007
Hi I am a newbie trying to learn normalization so kindly bear with me

Arent 2 Normal Form and 3 Normal Form the same

2NF:For a table to be in 2NF

The table should be in 1NF
There should be no duplication in the table,the columns with repeated data must be placed in another table.The table should consist of a foreign key to maintain a link between the two tables.

3NF:A table is said to be in 3NF if

It is in 2NF
Remove columns that are not fully dependent on the primary key.

In 2nf we are segregating the duplicated data and making another table by splitting the table in 2.

In 3nf we are again splitting the table to separate the columns which are not dependent on primary key.

Isnt this same as 2nf


Boyce codd normal form BCNF

A table is in BCNF if and only if for every one of its non trivial functional dependencies X->Y. X is either a candidate key or a super set.

I really dont understand this honestly.
Non trivial fucntional dependencies X->Y means ?
I understand functional dependency
if there is a table


If X is the primary key.
A and B are not dependent on X
Then A,B are put in another Table2

Table1{X,Y,Z} Table2{X,A,B}

is this right.

Kindly explain BCNF.


BillKent quoting E.F.Codd
Every non key attribute "must provide a fact about the key,the whole key and nothing but the key".

What does every non key attribute mean does it mean other than primary key.

Kindly answer my doubts.It will be very helpful in understanding further concepts.

Thank you.

I am a little confused kindly clear my doubts
Re: Doubts on Normalisation [message #377152 is a reply to message #377151] Sat, 20 December 2008 15:11 Go to previous messageGo to next message
Barbara Boehmer
Messages: 8610
Registered: November 2002
Location: California, USA
Senior Member
The following link has some examples that might make it clearer.

Re: Doubts on Normalisation [message #400394 is a reply to message #377151] Tue, 28 April 2009 00:55 Go to previous message
Michel Cadot
Messages: 63917
Registered: March 2007
Location: Nanterre, France, http://...
Senior Member
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Normalization Wiki page.

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