DATABASE

Question

Given the table R(x,y,z ) and fact that XY is the key ,give trivial functional dependency for R?

Answer 1

A→B is a trivial FD if A is super set of B ie. A ⊇ B

so here we go

xy → x

xy → y

xy →xy

Comments

trivial dependency can even exist on Non-Key attribute also.  I think even we have to include those here also? Please correct me if I am wrong.

xy -> ∅, is also Trivial FD.

Answer 2

Informally "Trivial" means very obvious.See it is very obvious that X->X.Similary,for the given question trivial means

xy → x

xy → y

xy →xy

Here RHS is subset of LHS.