Database Normalisation

Question 1

What is functional dependency?

Answer 1

Where A -> B would mean that there is no ambiguity of the value of B if A is given

Question 2

What is full functional dependency?

Answer 2

A -> B is full when B doesn’t depend on any proper subset of A

Question 3

How do you read dependency diagrams?

Answer 3

Arrows point from attributes to the attributes that are dependant on them

Question 4

What is 1st Normal Form? (1NF)

Answer 4

Each row contains only one value for each column, multi-valued attributes are in separate tables

Question 5

What is 2nd Normal Form? (2NF)

Answer 5

Relation in 1NF where every attribute is fully functionally dependent on the primary key

Question 6

What is transitive dependency?

Answer 6

If A -> B and B -> C C is transitively dependent on A via B

Question 7

What is 3rd Normal Form? (3NF)

Answer 7

Relation in 2NF where no attributes are transitively dependent on the primary key

Question 8

How do you make a schema into 2NF from 1NF?

Answer 8

Decompose schema along functional dependency on partial keys, with the partial key being a primary key of the new schema

Question 9

How do you make a schema into 3NF from 2NF?

Answer 9

Decompose along transitive dependency, with middle attributes as primary keys of new schemas