Free Keys, ER and normalization lessonsKeys, ER and normalization · Stage 2 · Functional dependencies · Step 1
Functional dependencies and closure
What 'A determines B' means, how to infer new dependencies, and how to compute an attribute set's closure. About 15 minutes.
With the FDs A → B and B → C, which of these is NOT implied?
- AC → A
- BA → C
- CA → BC
Show the answer
C → A. {C}⁺ is just {C}: nothing leads back to A.
4 questions on this idea
Short questions that apply the idea to new cases: trace it, work out a number, put steps in order. A wrong answer explains itself.
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