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3rd Normal Form -3NF

gudii9
gudii9 asked
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Last Modified: 2014-05-19
Hi,

I am going through below link
http://en.wikipedia.org/wiki/Third_normal_form


when and why to use the 3NF. I have not understood clearly what it is talking about esp with respect to Key and Codd. Please advice
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Commented:
People write entire books on logical and physical designs.  It will be hard to go into detail here.

You probably need to find another source other than Wikipedia to learn how to do a logical design.

Why use it:
It reduces stored redundant information.


When to use it:
You should always design the logical data model to at least 3NF.

Some will argue that the physical model should also be in 3NF.  I'm not sure I've ever seen a physical model in true 3NF.

Keys and Codd are easy:
Codd was sort of the createor of the rules for normalization.

Key is the unique identifier for an entity in the logical model and a primary key in the physical model.
Dave FordSoftware Developer / Database Administrator
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Commented:
You say "I have not understood clearly what it is talking about esp with respect to Key and Codd".

Does that mean you don't understand the concept of a primary key?  You don't know who E.F. Codd is ?

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Commented:
[Every] non-key [attribute] must provide a fact about the key,

what is meaning of this line. can you please elaborate. How non key must provide a fact about a key. It sounds strange to me.
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>>How non key must provide a fact about a key

In a nutshell:
Every attribute in an entity must be directly related to the key for the entity.

Remember the quote I posted in your other question that I said I wasn't going to tell you what it meant?  Well this is what it means...

Author

Commented:
Entity means Table right. Key means Primary key column right? Attribute(non-key) means non primary column? please advice about this terminology
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