This document discusses database normalization and its goals of eliminating data anomalies. It defines various normal forms including 1NF, 2NF, 3NF, and BCNF. 1NF requires each attribute to hold a single value. 2NF eliminates partial dependencies by requiring non-prime attributes to depend on the whole primary key. 3NF removes transitive dependencies by requiring non-key attributes to depend only on the primary key. BCNF further restricts dependencies such that each non-trivial dependency is on a super key. The document provides examples to illustrate functional and partial dependencies and how different normal forms address them.

1. Ms. Neethu Tressa
Assistant Professor
NORMALIZATION

2. CONTENTS
 INTRODUCTION
 DATABASE ANOMALIES
 FUNCTIONAL DEPENDENCY
 PARTIAL DEPENDENCY
 TRIVIAL DEPENDENCY
 TRANSITIVE DEPENDENCY
 NORMAL FORMS
 FIRST NORMAL FORM
 SECOND NORMAL FORM
 THIRD NORMAL FORM
 BOYCE-CODD NORMAL FORM

3. INTRODUCTION
 Normalization is a process of organizing the data in
database to avoid data redundancy, insertion anomaly,
update anomaly & deletion anomaly.

4. DATABASE ANOMALIES
 Update Anomaly – a record is updated, but other
appearances of the same items are not updated
 Insertion Anomaly – user is unable to insert a new
record when it should be possible to do so
 Deletion Anomaly – when a record is deleted, other
information that is tied to it is also deleted
 E.g.: Consider Employee Table
Emp-id Emp-name Emp-addr Emp-dept
101 Rick Delhi D001
101 Rick Delhi D002
123 Maggie Agra D890
166 Glenn Chennai D900
166 Glenn Chennai D004

5. FUNCTIONAL DEPENDENCY
 Functional Dependency, denoted by X→Y, holds if
whenever two tuples have the same value for X, they
must have the same value for Y.
 Attribute on the left hand side is known as the
determinant
 E.g.: Emp-name → E-mail
 Emp-name is a determinant of E-mail
Emp-name Project E-mail
Rick Smart System rick@yahoo.com
Glenn Management System glenn@gmail.com
Rick Re-design System rick@yahoo.com
Maggie Smart System maggie@yahoo.com
Glenn Database System glenn@gmail.com

6. PARTIAL DEPENDENCY
 Prime attribute − An attribute, which is a part of the
prime-key, is known as a prime attribute.
 Non-prime attribute − An attribute, which is not a part
of the prime-key, is said to be a non-prime attribute.
 A partial dependency is a situation where a non-prime
attribute is functionally dependent to a part of a prime-
key
 E.g.: Student-Project table
Stu-Id Proj-Id Stu-Name Proj-Name

7. TRIVIAL DEPENDENCY
 If a functional dependency FD X → Y holds, where Y
is a subset of X, then it is called a Trivial FD. Trivial
FDs always hold.
 If A and B are attributes of R,
 {A}→{A}
 {A,B} →{A}
 {A,B} →{B}
 {A,B} →{A,B} are all trivial FDs

8. TRANSITIVE DEPENDENCY
 If A, B, and C are attributes of relation R, such that
A → B, and B → C, then C is transitively dependent
on A
 E.g.: Student (stuId, Name, subject, credits, status)
with FD:
 credits→status
 By transitivity: stuId→credits , credits→status implies
stuId→status
 Transitive dependencies cause update, insertion,
deletion anomalies

9. NORMAL FORMS
 Most commonly used normal forms:
 First Normal Form (1NF)
 Second Normal Form (2NF)
 Third Normal Form (3NF)
 Boyce-codd Normal Form (BCNF)

10. FIRST NORMAL FORM (1NF)
 An attribute (column) of a table cannot hold multiple values.
It should hold only atomic values
 SELECT * FROM employee WHERE language LIKE ‘%English%’
 UPDATE employee SET language = ‘French, English’ WHERE
name = ‘George’
 Remove duplicate fields

11. SECOND NORMAL FORM (2NF)
 A relation is in second normal form (2NF) when it is in
1NF and when every non-key attribute, is fully
dependent on the primary key
 Remove Partial Dependency

12. SECOND NORMAL FORM (2NF) (Cont..)

13. SECOND NORMAL FORM (2NF) (Cont..)

14. THIRD NORMAL FORM (3NF)
 A relation is in third normal form (3NF) when it is in
2NF and all non-primary fields are dependent on the
primary key
 Remove Transitive Dependency

15. THIRD NORMAL FORM (3NF) (Cont..)

16. BOYCE-CODD NORMAL FORM (BCNF)
 A relation is in BCNF, if it is in 3NF and for every one of its
dependencies X → Y, one of the following conditions holds true:
 X → Y is a trivial functional dependency (i.e., Y is a subset of
X)
 X is a super key
 Remove determinants that are not super keys
Author Nationality Book title Genre Number of
pages
William
Shakespeare
English The Comedy of Errors Comedy 100
Markus
Winand
Austrian SQL Performance
Explained
Textbook 200
Jeffrey
Ullman
American A First Course in Database
Systems
Textbook 500
Jennifer
Widom
American A First Course in Database
Systems
Textbook 500

17. Author Nationality
William Shakespeare English
Markus Winand Austrian
Jeffrey Ullman American
Jennifer Widom American
Book title Genre Number of
pages
The Comedy of Errors Comedy 100
SQL Performance Explained Textbook 200
A First Course in Database Systems Textbook 500
Author Book title
William Shakespeare The Comedy of Errors
Markus Winand SQL Performance Explained
Jeffrey Ullman A First Course in Database Systems
Jennifer Widom A First Course in Database Systems
 Dependencies violating BCNF rules:
 author → nationality
 book title → genre, number of pages