normalisation

Question

A given relation is known to be in third normal form. Select the statement which can be inferred from this:

1. All attributes contribute to the primary key

2. Each non-key attribute determines the primary key

3. Each non-key attribute is determined by the primary key

4. Every determinant is a candidate key

5. The relation is not in fourth normal form.

please explain briefly as from my point of view 1,2,3,4 are correct.

 

Comments

what is the answer?

is it 3 only?

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Yes sir, answer is given as 3 only.

But why not 1,2,4……?

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Given that it is 3NF

 

1. All attributes contribute to the primary key

No need, let take R(A,B,C,D) and FD's are {A → BCD}

this is in 3NF but all attributes didn't contribute to the primary key

 

2.Each non-key attribute determines the primary key

Always False, if Attributes determines Primary Key, it is called as Candidate Key but not as Non-key

 

3. Each non-key attribute is determined by the primary key

Always true.

 

4. Every determinant is a candidate key

this statement conveying that in X → Y, X should be Candidate Key, it is for BCNF, for 3NF it is not necessary.

 

5.The relation is not in fourth normal form.

It is Not in syllabus, No comments on this statement.

Answer 1

any  one relation is in third normal form iff  a>b here a is super key or b is prime attribute from  this terminology first option is true,  2 also be true,3 also be true,4 also be correct,5 option may or may not be true

 

 

Comments

@Chandrabhan Vishwa 1

check my comment