Question

​​If a relation is in 2NF and 3NF forms then:

• A. no non-prime attribute us functionally dependent on other non-prime attribute
• B. no non-prime attribute is functionally dependent on prime attributes
• C. all attributes are functionally independent
• D. prime attribute is functionally independent of all non-prime attributes

Answer 1

I am confused by this question, why they ask 2NF and 3NF,

because 2NF is subset of 3NF

suppose in relation R(A,B,C,D,E,F): AB is Primary key and FS set as,

AB->C, A->D, D->E, B->F

option A. no non prime att. is functionally dependent on other non prime att

           this means transitive FD are not allowed, example. D->E not allowed.........this option seems correct by 3NF

option B. non prime att.  is functionally dependent on prime att.

          this is partial FD so no 2NF, example, A->D   --------------------wrong option

option C. in 2NF and 3NF there are dependencies between att. --------------------wrong option

option D. prime att is functionally independent of all non prime att.

               this could be the rule followed by 2NF

Answer 2

Option A is  correct i suppose because it tell about 3NF and once the relation is in 3NF it will definately be 2NF so i think (A).

Answer 3

(A) no non - prime attribute is functionally dependent on other non-prime attribute => No transitive dependency=> True

(B) No non prime attribute is functionally dependent on prime attribute = > No partial dependency => True

Answer 4

i think answer is C , if we consider a relation R(A,B) all functional dependencies as A tends to B and B tends to A all are fuctionally independent.

Comments

this situation is called functionally dependent