UHCL 23a Graduate Database Course - Minimal Covers Example

This video corresponds to the unit 5 notes for a graduate database (dbms) course taught by Dr. Gary D. Boetticher at the University of Houston - Clear Lake (UHCL). The theme is relational database theory. This video goes through an example on how to find a minimal cover for a set of functional dependencies.

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• Functional dependencies
• FDs
• Functionally determines
• logically implies
• x closure
• covers
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• relfexivity
• augmentation
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• minimal covers
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[nxjohny]

Just a short question: What should i do, if in the second step, when we eliminate the extraneous member of the left hand side, for example AB the left hand side, and the closure of A contain B and B closure contain A.

[GaryBoetticher]

@nxjohny You may eliminate either the A or the B. Given a set of FDs, there may be 2 more minimal covers.

[0rebelious0o]

For the final step, do you only look for redundant FDs with singles on the LHS? Still trying to form something containing the RHS in the closed set?

[orhancanceylan]

Thank you very much for that video ! But I have a question, after doing all of these steps, will the minimal cover also be a boyce codd normal form ? Or is each left side of the FDs a key ?

[sparklestar47]

thank you so much professor...!! it was so helpful for me!..

[harclevuyk]

Thnx a lot Professor . You are a great person . It was very hard for me to understand that using my professor's lessons . Blessed are those who give without remembering.

[danielrugeles]

Excellent. Thank you.

[heroclix0rz]

@kksandyrox You can always break an 'implies' statement down so that the left hand side implies each of the right hand sides individually.

So D-->AEH == D-->A, D-->E, D-->H.

Side Note:

It is NOT correct to say that: AEH-->D == A-->D, E-->D, H-->D.

The only exception is: AEH-->A == AE-->A == AH-->A == A-->A

[kksandyrox]

what if there are 3 elements on the right hand side? how to decompose and move forward? ex:

D-->AEH?

[teodorvb]

You just saved my live. This was the ultimate help.