• Trivial dependency:
  • A FD: X --> Y is trivial if and only if the right hand side is a subset of the left hand side.
  • In other words, a FD:  X --> Y is trivial if and only if Y   X, i.e. Y is contained in X.
  • Example:-

{cid, ano} -->  cid

  • Trivial dependencies are not much important from database design point of view.
  • Nontrivial dependency:
  • A FD: X-->Y is nontrivial if and only if the right hand side is not a subset of the left hand side.
  • In other words, a FD: X-->Y is nontrivial if Y is not contained in x.
  • Example:-

{cid, ano} -->access_date

  • Nontrivial dependencies are important from database design point of view.