For instance in the following example
Let be F={AB→C, B→D, CD→E, CE→GH, G→A}
Do we have AB→G?
We don't have any functional dependencies.
I am able to show a functional dependency when it works but how to show a counterexample when it doesn't?
relational-theory
For instance in the following example
Let be F={AB→C, B→D, CD→E, CE→GH, G→A}
Do we have AB→G?
We don't have any functional dependencies.
I am able to show a functional dependency when it works but how to show a counterexample when it doesn't?
Best Answer
To find if the functional dependency AB→G is implied by F you should find the closure of the attributes AB under F, i.e. AB+.
These are the steps:
and since G belongs to AB+, then AB→G can be derived from F.