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Data Mgmt Lab_Part_66

# Data Mgmt Lab_Part_66 - 196 Chapter 19 1 A → B 2 A →→...

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Unformatted text preview: 196 Chapter 19 1. A → B 2. A →→ B 3. BC → A 4. BC →→ A 5. B → C 6. B →→ C Answer 19.12 Answer omitted. Exercise 19.13 Consider a relation R with five attributes ABCDE . 1. For each of the following instances of R, state whether it violates (a) the FD BC → D and (b) the MVD BC →→ D : (a) { } (i.e., empty relation) (b) { ( a ,2,3,4,5), (2, a ,3,5,5) } (c) { ( a ,2,3,4,5), (2, a ,3,5,5), ( a ,2,3,4,6) } (d) { ( a ,2,3,4,5), (2, a ,3,4,5), ( a ,2,3,6,5) } (e) { ( a ,2,3,4,5), (2, a ,3,7,5), ( a ,2,3,4,6) } (f) { ( a ,2,3,4,5), (2, a ,3,4,5), ( a ,2,3,6,5), ( a ,2,3,6,6) } (g) { ( a ,2,3,4,5), ( a ,2,3,6,5), ( a ,2,3,6,6), ( a ,2,3,4,6) } 2. If each instance for R listed above is legal, what can you say about the FD A → B ? Answer 19.13 1. Note : The answer sometimes depends on the value of a. Unless otherwise men- tioned, the answer applies to all values of a. (a) { } (i.e., empty relation): does not violate either dependency. (b) { (a,2,3,4,5), (2,a,3,5,5) } : If a = 2, then BC → D is violated (otherwise it is not). BC →→ D is not violated (for any value of a) (c) { (a,2,3,4,5), (2,a,3,5,5), (a,2,3,4,6) } : BC → D is violated if a = 2 (otherwise not)....
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Data Mgmt Lab_Part_66 - 196 Chapter 19 1 A → B 2 A →→...

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