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Need help understanding the second and third normal forms

Posted on 2008-10-22
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Last Modified: 2012-05-05
I have two questions.
(1.) Besides needing to satisfy the first normal form, is the second normal applicable only to enitities/tables that have compound primary keys? Or can it be applicable to a table with only one primary key?

(3) What is the third normal form? Is it basically saying that no Non Key attributes must not be dependent upon each other?

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Question by:brgdotnet
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by:David Robitaille
David Robitaille earned 30 total points
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1- It can it be applicable to a table with only one primary key, yes, it<s just remove the "duplicate", the street exemple is good, we got a database where the same street is not always spelled the same.
2 - (or 3) basicly it s that.
 
here some bonus links
http://databases.about.com/od/specificproducts/a/firstnormalform.htm
http://databases.about.com/od/specificproducts/a/2nf.htm
http://databases.about.com/od/specificproducts/a/3nf.htm
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dportas earned 50 total points
ID: 22781277
(1) No. 2NF is a rule that can apply to any relation.
(2) ?
(3) Very loosely speaking you are right.

The most important normal forms are BCNF and 5NF. 2NF and 3NF are somewhat weaker rules about functional dependencies. Since they are subsumed by BCNF it's arguable that 2NF and 3NF are not very important. In fact what many people refer to as 3NF is really BCNF - the definitions are often confused.
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by:David Robitaille
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I agree with dportas
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