How do you find the minimal cover of functional dependencies?

How do you find the minimal cover of functional dependencies?

There can be many such minimal covers for a set of functional dependencies F….Simple properties/steps of minimal cover:

1. Right Hand Side (RHS) of all FDs should be single attribute.
2. Remove extraneous attributes. [What is extraneous attribute? Refer here].
3. Eliminate redundant functional dependencies.

How do I reduce functional dependency?

Remove all redundant functional dependencies. without making use of the f.d. we are testing and check whether Y is a part of the closure. If yes, then the f.d. is redundant….Now, do the same for G.

1. Create a singleton right hand side.
2. Remove all extraneous attributes.
3. Remove all redundant functional dependencies.

How do I get rid of functional dependency?

Step 1: Start with a set of S of functional dependencies (FDs). Step 2: Remove an FD f and create a set of FDs S’ = S – f . Step 3: Test whether f can be derived from the FDs in S’; by using the set of Armstrong’s axioms and derived rules. Step 4: If f can be so derived, it is redundant , and hence S’ = S.

How to find canonical cover of functional dependencies?

Consider the following set F of functional dependencies: Steps to find canonical cover: A BC. Now, the revised set F becomes: There is an extraneous attribute in AB C because even after removing AB C from the set F, we get the same closures.

How to logically imply all functional dependencies in?

F logically implies all dependencies in . No functional dependency in contains an extraneous attribute. Each left side of a functional dependency in is unique. That is, there are no two dependencies and in such that . repeat 1. Use the union rule to replace any dependencies in and with . 2.

Can a functional dependency be removed from the LHS?

Consider any functional dependency XY Z. If X in itself can determine Z, then the attribute Y is extraneous and can be removed. As we can see, the occurrence of extraneous attributes is possible only in those functional dependencies where there are more than one attributes in the LHS.

When is F a minimal cover of G?

F is a minimal cover of G if F is the smallest set of functional dependencies that cover G. We won’t 4. prove it, but every set of functional dependencies has a minimal cover. Also, note that there may be more than one minimal cover. We nd the minimal cover by iteratively simplifying the set of functional dependencies.