1. ITS232 Introduction To Database Management Systems
CHAPTER 5
Normalization Of Database Tables
(Part I: Concept & Process)
Siti Nurbaya Ismail
Faculty of Computer Science & Mathematics,
Universiti Teknologi MARA (UiTM), Kedah
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2. Chapter 5: Normalization Of Database Tables
5.0 Normalization Of Database Tables 5.1 Database Tables And Normalization 5.2 The Need For Normalization 5.3 The Normalization Process 5.4 Normalization And Database Design 5.5 Denormalization

3. Chapter 5: Normalization Of Database Tables 5
Chapter 5: Normalization Of Database Tables 5.1 Database Tables And Normalization
Table is the basic building block of database design
ER Modeling, yields good table structures, but it is still possible to create poor table structures even in a good database design
How do you recognize a poor tables structure, and how do you produce good table?
Normalization
A process of evaluating and correcting table structures to minimize data redundancies, thereby reducing the possibility of data anomalies
Works through a series of stages called normal forms

4. Chapter 5: Normalization Of Database Tables 5
Chapter 5: Normalization Of Database Tables 5.1 Database Tables And Normalization
In Chapter 4, ER Modeling, we have adopted a top-down approach to database design that begins by identifying the entities and relationship
Normalization is a bottom-up approach to database design that begins by examining the relationships between attributes

5. Chapter 5: Normalization Of Database Tables 5
Chapter 5: Normalization Of Database Tables 5.1 Database Tables And Normalization
Top-down
Conceptual
Model
Entity
Attribute
Bottom-up
{ ER Modeling }
{ Normalization }

6. Chapter 5: Normalization Of Database Tables 5
Chapter 5: Normalization Of Database Tables 5.1 Database Tables And Normalization
EMPLOYEE
name
salary
city
branchNO
has M 1
BRANCH
position
employeeNO
branchNO*
EMPLOYEE
BRANCH
employeeNO
name
position
salary
branchNO
S21
Johan
Manager
3000
B005
S37
Ana
Assistant
1200
B003
S14
Daud
Supervisor
1800 S9
Mary
900
B007 S5
Siti
2400
S41
Jani
branchNO
city
B005
Kepong
B007
Nilai
B003
PTP
BRANCH(branchNO,city)
EMPLOYEE(employeeNO,name,position,salary,branchNO*)

7. Chapter 5: Normalization Of Database Tables 5
Chapter 5: Normalization Of Database Tables 5.2 The Need For Normalization
Normalization is typically used with ER Modeling
There are two common situations in which database designers use normalization:
Designing a new database
When designing a new database structure based on the business requirements of the end users, the database designer will construct a data model using technique such as Crow’s Foot notation ERDs
After the initial design is complete, the designer can used normalization to analyze the relationships that exist among the attributes within each entity, to determine if the structure can be improved through normalization

8. Chapter 5: Normalization Of Database Tables 5
Chapter 5: Normalization Of Database Tables 5.2 The Need For Normalization
Normalization is typically used with ER Modeling
There are two common situations in which database designers use normalization:
Modifying existing data structures
Sometimes database designer are asked to modify existing data structures that can be in form of flat files, spreadsheet, or older database structures
Normalization process can be used to analyze the relationship among the attributes or fields in the data structures, to improve the existing data structure in order to create an appropriate database design

9. Chapter 5: Normalization Of Database Tables 5
Chapter 5: Normalization Of Database Tables 5.2 The Need For Normalization
There for in both situations describe, the need for normalization are:
to analyze the relationship among the attributes or fields in the data structures
to improve the existing data structure in order to create an appropriate database design
Normalization
A process of evaluating and correcting table structures to minimize data redundancies, thereby reducing the possibility of data anomalies

10. Chapter 5: Normalization Of Database Tables 5
Chapter 5: Normalization Of Database Tables 5.3 The Normalization Process
When we design a database, the main objective is to create an accurate representation of data, relationship between the data, and constrains on the data that is relevant.
To achieve this objective, we have to identify suitable set of relations (table) by creating good table structure.
Normalization
A process of evaluating and correcting table structures to minimize data redundancies, thereby reducing the possibility of data anomalies
Works through a series of stages called normal forms

11. Chapter 5: Normalization Of Database Tables 5
Chapter 5: Normalization Of Database Tables 5.3 The Normalization Process
The most commonly used normal forms:
First Normal Form (1NF)
Second Normal Form (2NF)
Third Normal Form (3NF)
2NF is better than 1NF; 3NF is better than 2NF
Highest normalization is not always desirable; joint vs redundancy
For most business database design purposes, 3NF is as high as we need to go in normalization process

12. Chapter 5: Normalization Of Database Tables 5
Chapter 5: Normalization Of Database Tables 5.3 The Normalization Process
Every normal form is based on functional dependencies between attributes in a relationship
Each relationship can be normalized into a specific form to avoid anomalies
Anomalies?
anomaly = abnormality
ideally a field value change, should be made only in a single place
Data redundancy, however, fosters an abnormal condition by forcing field value changes in many different locations
Insertion anomalies
Deletion anomalies
Modification anomalies

13. Chapter 5: Normalization Of Database Tables 5
Chapter 5: Normalization Of Database Tables 5.3 The Normalization Process
Formal technique for analyzing relations based on their Primary Key (or candidate keys) and functional dependencies
The technique executed as a series of steps (stage). Each step corresponds to a specific normal form, that have specific characteristic
As normalization proceeds, the relations become progressively more restricted (stronger) in format and also less vulnerable to anomalies
Data Redundancies
0NF/UNF
1NF
2NF
3NF
Normalization
Denormalization

14. Chapter 5: Normalization Of Database Tables 5
Chapter 5: Normalization Of Database Tables 5.3 The Normalization Process
Relationship between normalization form
Denormalization
Figure 1: Diagrammatic illustration of the
relationship between the normal forms
Normalization

15. Chapter 5: Normalization Of Database Tables 5
Chapter 5: Normalization Of Database Tables 5.3 The Normalization Process
Data Sources
Users
Users’ requirements
specification
Forms/reports that are used or generated by the enterprise
Sources describing the enterprise such as data dictionary and corporate data model
Transfer attributes into table format
Unnormalized Form (UNF)
Remove repeating group
First Normal Form (1NF)
Remove partial dependencies
Second Normal Form (2NF)
Remove transitive dependencies
Third Normal Form (3NF)

16. Chapter 5: Normalization Of Database Tables 5
Chapter 5: Normalization Of Database Tables 5.3 The Normalization Process
Normalization Process
Relation/table Format
Have repeating group -PK not defined
UNF
1)Repeat Group
2)PK is not defined
(1 Table)
1NF
1)Remove Repeat Group
2)Defined PK  composite PK consist of attributes
(1 or 2 Tables)
No repeating group -PK defined -Test partial dependency
Test for partial dependency
If (exist)
(2 or 3 Tables)
(more then 1 table)
(a b …. TD) 1
(a  ……. TD) 2
(b  ….… TD) 3
2NF
No repeating group -PK defined -No partial dependency -Test transitive dependency
Test for transitive dependency
If (exist)
(a, b  x, y)
(a c, d)
(b  z)
(c  d)
No repeating group -PK defined -No partial dependency -No transitive dependency
3NF
(3 or 4 Tables)

17. Chapter 5: Normalization Of Database Tables 5
Chapter 5: Normalization Of Database Tables 5.3 The Normalization Process
Functional Dependencies
An important concept associated with normalization is functional dependency which describes the relationship between attributes
In this section, you will learn about functional dependency and then focus on the particular characteristics of functional dependency that are useful for normalization

18. Chapter 5: Normalization Of Database Tables 5
Chapter 5: Normalization Of Database Tables 5.3 The Normalization Process
Characteristic Of Functional Dependencies
For the discussion on functional dependency, assume that a relational schema has attributes (A,B,C,….Z) and that the database is describe by a single universal relation called R=(A,B,C,…,Z). This assumption means that every attribute in the database has a unique name
Functional dependencies:
Describe the relationship between attributes in a relation. For example,
if A and B are attributes of relation R, B is functionally dependent on A (denoted A  B), if each value of A is associated with exactly one value of B. (A and B may each consist of one or more attributes.)

19. Chapter 5: Normalization Of Database Tables 5
Chapter 5: Normalization Of Database Tables 5.3 The Normalization Process
Characteristic Of Functional Dependencies
Consider a relation with attributes A and B, where attribute B is functionally dependent on attribute A
To describe the relationship between attributes A and B is to say that A functionally determines B
R(A,B)
A  B A B
B is functionally
dependent on A

20. Chapter 5: Normalization Of Database Tables 5
Chapter 5: Normalization Of Database Tables 5.3 The Normalization Process
Characteristic Of Functional Dependencies
When a functional dependency exist, the attribute or group of attributes on the left-handed side of the arrow is called determinant A B
B is functionally
dependent on A
Determinant:
Refers to the attribute, or a group of attributes, on the
left handed side of the arrow of a functional dependency

21. Chapter 5: Normalization Of Database Tables 5
Chapter 5: Normalization Of Database Tables 5.3 The Normalization Process
Characteristic Of Functional Dependencies
EMPLOYEE
BRANCH
employeeNO
name
position
salary
branchNO
S21
Johan
Manager
3000
B005
S37
Ana
Assistant
1200
B003
S14
Daud
Supervisor
1800 S9
Mary
900
B007 S5
Siti
2400
S41
Jani
branchNO
city
B005
Kepong
B007
Nilai
B003
PTP
BRANCH(branchNO,city)
EMPLOYEE(employeeNO,name,position,salary,branchNO*)

22. Chapter 5: Normalization Of Database Tables 5
Chapter 5: Normalization Of Database Tables 5.3 The Normalization Process
Unnormalized Form (UNF)/(0NF)
A table that contains one or more repeating groups
To create an unnormalized table
Transform the data from the information source (e.g. form) into table format with columns and rows

23. employeeNO functionally
Chapter 5: Normalization Of Database Tables 5.3 The Normalization Process
Characteristic Of Functional Dependencies
Consider the attributes employeeNO and position of the EMPLOYEE relation
For a specific employeeNO(S21), we can determine the position of that member of employee as Manager
employeeNO functionally determines position
employeeNO
position
employeeNO functionally
determines position
S21
Manager

24. position does not functionally
Chapter 5: Normalization Of Database Tables 5.3 The Normalization Process
Characteristic Of Functional Dependencies
However the next figure illustrate that the opposite is not true, as position does not functionally determines employeeNO
A member of employee holds one position; however, they maybe several members of employee with the same position
position
employeeNO
position does not functionally
determine emlpoyeeNO
Manager
S21 S5

25. Chapter 5: Normalization Of Database Tables 5
Chapter 5: Normalization Of Database Tables 5.3 The Normalization Process
Characteristic Of Functional Dependencies
Functional dependency can be describe by two types:
Full functional dependency (Partial dependency)
Will be used to transform 1NF  2NF
Transitive dependency
Will be used to transform 2NF  3NF

26. Chapter 5: Normalization Of Database Tables 5
Chapter 5: Normalization Of Database Tables 5.3 The Normalization Process
Characteristic Of Functional Dependencies
Functional dependency can be describe by two types:
Full functional dependency (Partial dependency)
Full functional dependency indicates that if A and B are attributes of a relation, B is fully functionally dependent on A, if B is functionally dependent on A, but not on any proper subset of A
R(A,B,C)
A  B,C

27. Chapter 5: Normalization Of Database Tables 5
Chapter 5: Normalization Of Database Tables 5.3 The Normalization Process
Characteristic Of Functional Dependencies
Functional dependency can be describe by two types:
Transitive dependency
A, B and C are attributes of a relation such that if A  B and B  C, then C is transitively dependent on A through B (Provided that A is not functionally dependent on B or C)
R(A,B,C)
A  B
B  C

28. Chapter 5: Normalization Of Database Tables 5
Chapter 5: Normalization Of Database Tables 5.3 The Normalization Process
First Normal Form (1NF)
A relation in which the intersection of each row and column contains one and only one value
A relation is in 1NF if every attribute for every tuple have a value and domain for each attribute can not be simplified anymore

29. Chapter 5: Normalization Of Database Tables 5
Chapter 5: Normalization Of Database Tables 5.3 The Normalization Process
Second Normal Form (2NF)
A relation that is in 1NF and every non-PK attribute is fully functionally depends on the PK
Based on the concept of partial dependency (dependencies' based on only a part of composite PK)
2NF applies to relations with composite keys, that is, relations with PK composed of two or more attributes
A relation with a single-attribute PK is automatically in at least 2NF

30. Chapter 5: Normalization Of Database Tables 5
Chapter 5: Normalization Of Database Tables 5.3 The Normalization Process
Third Normal Form (3NF)
A relation that is in 1NF and 2NF and which no non-PK attribute is transitively dependent on the PK
Based on the concept of transitive dependency, where;
A, B and C are attributes of a relation such that if A  B and B  C then C is transitively dependent on A through B
(Provided that A is not functionally dependent on B or C)
3NF applies to relations with transitive dependency
A relation that have no transitive dependency are already in 3NF

31. Chapter 5: Normalization Of Database Tables 5
Chapter 5: Normalization Of Database Tables 5.3 The Normalization Process
UNF To 1NF
Nominate an attribute or group of attributes to act as the key for the unnormalized table
Identify the repeating group(s) in the unnormalized table which repeats for the key attribute(s), remove the repeating group by
entering appropriate data into the empty columns of rows containing the repeating data
Fill the blanks by duplicating the non repeating data, where required
This approach is commonly referred to as ”flattening table”
This approach will produce redundancy in a relationship, but it can be eliminated in higher normalization process

32. Chapter 5: Normalization Of Database Tables 5
Chapter 5: Normalization Of Database Tables 5.3 The Normalization Process
1NF To 2NF
Identify the primary key for the 1NF relation
Identify the functional dependencies in the relation.
Draw functional dependencies diagram
Write functional dependencies in relational schema
If partial dependencies exist on the primary key remove them by placing them in a new relation along with a copy of their determinant

33. Chapter 5: Normalization Of Database Tables 5
Chapter 5: Normalization Of Database Tables 5.3 The Normalization Process
2NF To 3NF
Identify the primary key in the 2NF relation
Identify functional dependencies in the relation
If transitive dependency exist on the PK, remove them by placing them in a new relation along with a copy of their determinant
Guidelines:
R (A, B, C) with transitive dependencies:
A  B
B  C
Simplified R to:
R1 (A, B*)
R2 (B, C)

34. Chapter 5: Normalization Of Database Tables 5
Chapter 5: Normalization Of Database Tables 5.4 Normalization & Database Design
Normalization should be part of the design process.
Make sure the proposed entities meet the required normal form before the table structures are created
Be aware of good design principles and procedures as well as normalization procedures
ERD: is created by interactive process, begin by identifying relevant entities, their attributes, and their relationship. ERD provides the big picture/macro view, of an organization’s data requirements & operations.
Normalization: focuses on the characteristics of specific entities: that is represents macro view of the entities within the ERD
Therefore the two techniques are used in an iterative and incremental process

35. Chapter 5: Normalization Of Database Tables 5.5 Denormalization
Data Redundancies
0NF/UNF
1NF
2NF
3NF
Normalization
Denormalization