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This is relational databases question

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Consider the relation schema R-A, B, C, D) with an unknown set of functional dependencies 4.1 What is the maximum number of (candidate) keys that R may have? Design a set of functional depen- (2 dencies on R to achieve the maximum number of (candidate) keys. Justify your answers. Mark)

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Answer #1

The maximum number of candidate keys that R may have is 4. This will represent the case when knowing just one value out the four columns, we can determine all the other ones. That is, every column can be determined by using the value of any other column.

Set of functional dependencies will be :

A --> B
B --> C
C --> D
D --> A

Clearly, by knowing just one of A / B / C / D, we can reach any other directly or indirectly.

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