Lecture 2 - Functional Dependency

Question 1

What is functional dependency?

Answer 1

is a formal metric of the degree of goodness of relational schema.

-> functional dependency is a constraint derived from the relationship between attributes

Question 2

What is functional dependency in simple terms?

Answer 2

Given a relation, an attribute X functionally determines an attribute
Y, if a value of X determines a unique value for Y. i.e. X can determine Y

Question 3

Notation for functional dependency (e.g. X to Y)?

Answer 3

X->Y

Question 4

Mathematical form of functional dependency?

Answer 4

for any two tuples t1 and t2:
If t1[X] = t2[X] then t1[Y] = t2[Y]

Question 5

Functional dependency is specific over how many tuples in a relation?

Answer 5

All of them

Question 6

Candidate Key Principle of FD?

Answer 6

If K is a Candidate Key, then K should functionally determine
all attributes in relation R

Question 7

Decomposition rule for FD?

Answer 7

If X -> {Y,Z} then X -> Y and X -> Z

Question 8

Additive rule for FD?

Answer 8

If X -> Y and X -> Z then X -> {Y,Z}

Question 9

Transitive rule for FD?

Answer 9

If X → Y and Y → Z then X → Z

Question 10

Reflexive rule for FD?

Answer 10

If Y ⊆ X then X → Y

Question 11

Augmentation rule for FD?

Answer 11

If X → Y then X U {Z} → Y U {Z}

Question 12

What does -> mean?

Answer 12

implication

Question 13

What does <-> mean?

Answer 13

equivalence