Flashcards in Week 10 UAS Deck (13):

1

## Purpose of Normalization?

###
Normalization is a technique for producing a set of suitable relations that support the data requirements of an enterprise.

Characteristics of a suitable set of relations include:

- the minimal number of attributes necessary to support the data requirements of the enterprise;

- attributes with a close logical relationship are found in the same relation;

- minimal redundancy with each attribute represented only once with the important exception of attributes that form all or part of foreign keys.

2

## Types of update anomalies include?

###
Types of update anomalies include:

1. Insertion

2. Deletion

3. Modification

3

## Two important properties of decomposition?

###
1. Lossless-join property enables us to find any instance of the original relation from corresponding instances in the smaller relations.

2. Dependency preservation property enables us to enforce a constraint on the original relation by enforcing some constraint on each of the smaller relations.

4

## UNF (Unnormalized Form)

### A table that contains one or more repeating groups.

5

## 1NF (First Normal Form)

### A relation in which the intersection of each row and column contains one and only one value.

6

## 2NF (Second Normal Form)

### A relation that is in 1NF and every non-primary-key attribute is fully functionally dependent on the primary key.

7

## 3NF (Third Normal Form)

### A relation that is in 1NF and 2NF and in which no non-primary-key attribute is transitively dependent on the primary key.

8

## Functional Dependencies?

###
Functional dependency describes relationship between attributes.

For example, if A and B are attributes of relation R, B is functionally dependent on A, if each value of A in R is associated with exactly one value of B in R.

9

## What is Armstrong's axioms?

###
a set of inference rules, specifies how new functional dependencies can be inferred from given ones.

Armstrong’s axioms are as follows:

(1) Reflexivity

If B is a subset of A, then A → B

(2) Augmentation

If A → B, then A,C → B,C

(3) Transitivity

If A → B and B → C, then A → C

(4) Self-determination A→A

(5) Decomposition

If A → B,C, then A → B and A → C

(6) Union

If A → B and A → C, then A → B,C

(7) Composition

If A → B and C → D then A,C → B,D

10

## What is Boyce-Codd Normal Form (BCNF)?

### A relation is in BCNF if and only if every determinant is a candidate key.

11

## Multi-Valued Dependency (MVD)

### Represents a dependency between attributes (for example, A, B, and C) in a relation, such that for each value of A there is a set of values for B and a set of values for C. However, the set of values for B and C are independent of each other.

12

## Fourth Normal Form (4NF)

### A relation is in 4NF if and only if for every nontrivial multivalued dependency A ->> B, A is a candidate key of the relation.

13