CODEWITHSUNDEEP
databasenormalization3nf
eccentricCoder
eccentricCoder

Reputation: 844

Is the relation in 3NF?

R(ABCD) with FD's

AB -> CD BC -> D

I found this question in a book and it says the relation is in 2nf but not in 3nf.

I cant find any trivial dependencies and also no non prime attribute is functionally dependent on another non prime attribute then how come the relation is not in 3nf?

Should i consider BC as a non prime attribute too? Please help me understand the concept of 3NF

I have one more doubt

If the functional depenencies are

AB -> CD, C -> A, A -> C

Will the relation be in 3NF? or will it violate 2NF because A -> C shows that C is not fully functionally dependent on AB?

Upvotes: 0

Views: 259

Answers (1)

Lordferrous
Lordferrous

Reputation: 716

Let me explain in simple words:

Condition for Second normal form:

It is in first normal form

All non-prime attributes are fully functional dependent on the super key

Condition for Third normal form:

It is in second normal form

All non-key attributes must depend only on super key

 Note:2NF allows non-prime attribute to depend on non-prime but 3NF does not allows it

In the given relation: AB -> CD BC -> D

AB is a prime attribute

C,D are non-prime attribute

It is not in Third normal form because, D is a non-prime attribute which is not dependent on super-key AB

So,it is in 2NF and not in 3NF

Hope,it helps

Upvotes: 1

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