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gudii9
asked on
5/14/2014
3rd Normal Form -3NF
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
Oracle Database
DB2
Databases
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Last Comment
slightwv (䄆 Netminder)
8/22/2022 - Mon
slightwv (䄆 Netminder)
5/14/2014
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.
Member_2_2484401
5/14/2014
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 ?
-- DaveSlash
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momi_sabag
5/14/2014
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gudii9
5/14/2014
ASKER
[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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slightwv (䄆 Netminder)
5/14/2014
>>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...
gudii9
5/14/2014
ASKER
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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slightwv (䄆 Netminder)
5/14/2014
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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.