Friday, 9 December 2016

What is meant by full functional dependency

Define full functional dependency / When would you say that an attribute is fully functionally dependent on other attributes? / What is full functional dependency?

Full Functional Dependency

In a functional dependency A  B, (A is a set of attributes and B is another set of attributes), the dependency where B is fully dependent on A, and not on any of the subset of A is called Full Functional dependency. For example, assume that attributes P and Q together can only uniquely identify the value of the other attribute R. Then, PQ R is Full Functional Dependency. 

As another example, let us consider the set F of functional dependencies; F = { B, AD B }. In this case, the FD B is full functional dependency whereas AD B is not full, that is B is not fully functionally dependent on AD, instead it depends on A alone.

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