Question #50242

Given the following relational instance,

A B C

1 2 3

3 1 2

1 3 2

4 1 5

Which of the following functional dependencies are

satisfied?

i) A -> B

ii) B -> C

iii) A-> C

A B C

1 2 3

3 1 2

1 3 2

4 1 5

Which of the following functional dependencies are

satisfied?

i) A -> B

ii) B -> C

iii) A-> C

Expert's answer

A functional dependency is a constraint between two sets ofattributes in a relation from a database.

Given a relation R, a set ofattributes X in R is said to functionally determine another

set of attributes Y, also in R, (written X → Y) if,

and only if, each X value is associated with precisely one Y

value; R is then said to satisfy the functional

dependency X → Y.

So, in our case, dependency A-> C is

satisfied.

That's why, the right answer is

iii) A-> C

Given a relation R, a set ofattributes X in R is said to functionally determine another

set of attributes Y, also in R, (written X → Y) if,

and only if, each X value is associated with precisely one Y

value; R is then said to satisfy the functional

dependency X → Y.

So, in our case, dependency A-> C is

satisfied.

That's why, the right answer is

iii) A-> C

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