ACE-test

Question

Answer 1

$$\begin{align*} &FD's = \left \{ \text{AC}\rightarrow BD \text{ , AD}\rightarrow B \right \} \\ \\ &\text{CK } = AC \;\;\;\; \text{because} \left ( AC \right )^{+} = \left \{ A,B,C,D \right \} \\ \\ \end{align*}$$

Comments

Hello..I have a doubt.The question gives relation R(A,B,C) ,can we derive a dependency if attribute not present.Like here AD -->B here,is this dependency valid in this relation?

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Here D is not present in relation(A,B,C). How to deal with it?