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databasekeyfunctional-dependencies

Concept Check -- Key Determination from Functional Dependencies

This is more of a concept check than anything, but suppose I have a relation R on attributes ABCD with the functional dependencies B -> ACD and C -> D. The solitary key for this relation is B, and a superkey for this relation is BC, correct?

Solution

  • The only candidate key in your example is indeed B. Any collection of attributes containing B will be a superkey, e.g., B itself, AB, BC or ABD.