Consider the following proposed rule for functional dependencies: If and , then . Prove that this rule is not sound by showing a relation r that satisfies and , but does not satisfy .
| 1 | 6 | 7 |
| 2 | 3 | 5 |
| 2 | 4 | 5 |
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Consider the following proposed rule for functional dependencies: If α→β and γ→β, then α→γ. Prove that this rule is not sound by showing a relation r that satisfies α→β and γ→β, but does not satisfy α→γ.
| α | γ | β |
|---|---|---|
| 1 | 6 | 7 |
| 2 | 3 | 5 |
| 2 | 4 | 5 |