- Functional Dependency :
- Let attributes X and Y are two subsets of attributes of relation R.
- If the values of the X component of a tuple uniquely (or functionally) determine the values of the Y component, then, there is a functional dependency from x to Y.
Input: Let F be a set of FDs for relation R.
Let f: A B is a FD to be examined for redundancy.
- F’ = F – f
- T = A
- For each FD: xy in F’ Do
- If X subsetT Then
T = T Y
4. If B subsetT Then
f: A B is redundant.
- Output: Decision whether a given FD f: A B is redundant or not.
- Once a set of FDs for any relation R is given, it may be possible that this set contains redundant FDs.
- “ A FD in the set is redundant, if it can be derived from the other FDs in the set”.
- This algorithm is known as membership algorithm.
- A set of functional decencies F for relation R is called Minimal or Irreducible cover of asset of functional dependencies, if it does not have any redundant functional dependency.