This write-up is the suggested lecture notes for a second level course on advanced topics in database systems for master's students of Computer Science with a theoretical focus. A prerequisite in algorithms and an exposure to database systems are required. Additional reading may require exposure to mathematical logic. The starting point for these notes are from M.Y.Vardi's survey listed herein as a reference - some of the proofs are presented as such . This select rewrite on functional dependency is intended to provide a few clarifications even though radically new design approaches are now being proposed.