Is this partial dependency?

Question

I have this relation:

R = ABCDE
F: AB->DE, AC->B, DE->C, AE->C, C->AB.

Is AC->B a partial dependency in F?

I'm guessing it is, because

C->AB can be decomposed to

C->A
C->B

from where we can conclude that there exists a subset of AC (C in our case) which goes into B, that is

C->B.

I couldn't find a formal definition on the internet, so I would like it if someone could confirm my assumption.

Answer 1

In order for AC->B to be a partial key dependency, it has to satisfy these conditions.

• AC must be a candidate key. (Not necessarily the primary key.)

• One of these functional dependencies must hold.

  • A->B, or
  • C->B

So the first question I'd ask myself is, "Is AC a candidate key of F?"