title: Is x--->y a trivial functional dependency?
body: <p>If y is a subset of x then x--&gt;y is trivial functional dependency (it is well known). But I have doubt: y is not subset of x and x U y = R, then can I say x--&gt;y is a trivial functional dependency.( I read it in some article)</p>
  <p>Adding to above question: Why X U Y = R holds in case of multivalued dependencies(trivial)? Can somebody give an example so that I can understand?</p>