Self Doubt

Question

While checking for normal forms 

Why we only check conditions only on F not on F+

eg R(A,B,C) F = {A->B , B->C} is in 3NF or not ?

We will apply defination of 3NF i,e either LHS should be super key or RHS should be prime attribute ON ALL FDs IN F OR  F+ ??

Similarly in decomposition, to check if decomposed relation is in particular normal form we apply check on ALL IMPLIED FDs from F ??

In below ex should all implied FDs be checked ??

 

Comments

you just need to apply on F, it will automatically take care of F⁺.

A --> B, and B ---> C

if A is Key, then A ---> C ( inferred from the above FD's ) also valid.

 

if X --> Y and Y is Prime attribute then let Z --> X ===> Z ---> Y ( inferred from the above FD's ) also valid.