以下关系中的候选键是什么

Question

R(A,B,C,D,E) Functional Dependencies = {AC->E,B->D,E->A}

I know ABC is a candidate key.Can BC be a candidate key too?

Answer 1

The definition of "candidate key" is a superkey that does not contain another superkey. So a candidate key does not contain another candidate key.

Answer 2

I could tell that BC is not a candidate key. For (ABC)+, you could get the attribute D and E through the functional dependency and thus you get a key by involving all the attributes.

However, for (BC)+, you could only get D, you cannot get A or E. Thus, BC is not a candidate key.