Data Design
Normalization
- Mr. Ahmad Al-Ghoul
learning Objectives
 Explain the concept of
normalization
2
A Normalization Example

The three steps of data normalization are



Remove all repeating groups and identify the
primary key
Ensure that all nonkey attributes are fully
dependent on the primary key
Remove any transitive dependencies,
attributes which are dependent on other
nonkey attributes
3
A Normalization Example

A Normalization Example


To show the normalization process, consider the familiar
situation which might depict several entities in a school advising
system: ADVISOR, COURSE, and STUDENT
The relationships among the three entities are shown in the ERD
below
[1]
4
A Normalization Example



In this example we will discuss the normalization rules
for these three entities, to show how you can design a
validate ERD
Note that the relationship between student and course is
many to many relationship (M:N) which can not create
physically and as we said previously we must solve this
problem by dividing this relationship to two one to many
(1:M) relationship by adding a new entity called
Associative entity
the STUDENT table contains fields that relate to the
ADVISOR and COURSE entities, so you can decide to
begin with the initial design for the STUDENT table.
5
A Normalization Example

Unnormalized student table

STUDENT (STUDENT-NUMBER, STUDENT-NAME, TOTALCREDITS, GPA, ADVISOR-NUMBER, ADVISOR-NAME,
(COURSE-NUMBER, COURSE-DESC, NUM-CREDITS,
GRADE))
Repeating
groups
The STUDENT table is unnormalized because it contains a repeating group
that represents the courses each student has taken. [1]
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A Normalization Example

1NF


To convert the STUDENT record to 1NF, you
must expand the primary key to include the
key of the repeating group
STUDENT (STUDENT-NUMBER, STUDENTNAME, TOTAL-CREDITS, GPA, ADVISORNUMBER, ADVISOR-NAME, COURSE-NUMBER,
COURSE-DESC, NUM-CREDITS, GRADE)
7
A Normalization Example
Choose data items
Identify keys
Split groups
Eliminate repeating groups
UNF
STUDENT-NUMBER,
STUDENT-NAME,
TOTAL-CREDITS,
GPA,
ADVISOR-NUMBER,
ADVISOR-NAME,
COURSE-NUMBER,
COURSE-DESC,
NUM-CREDITS,
GRADE
UNF to 1NF
level
1
1
1
1
1
1
2
2
2
2
1NF
STUDENT-NUMBER,
STUDENT-NAME,
TOTAL-CREDITS,
GPA,
ADVISOR-NUMBER,
ADVISOR-NAME,
COURSE-NUMBER,
COURSE-DESC,
NUM-CREDITS,
GRADE
8
A Normalization Example
The STUDENT table in 1NF. Notice that the primary key has been
expanded to include STUDENT-NUMBER and COURSE-NUMBER. Also,
the repeating group has been eliminated.
[1]
9
A Normalization Example

2NF

No attribute dependent on a portion of a
primary key
The student name, total credits, GPA, advisor
number, and advisor name all relate only to the
student number
 The course description depends on the course
number
 Grade field depends on the entire primary key

10
A Normalization Example
Does this attribute
depend on the whole
of the primary key?
1NF
STUDENT-NUMBER,
STUDENT-NAME,
TOTAL-CREDITS,
GPA,
ADVISOR-NUMBER,
ADVISOR-NAME,
COURSE-NUMBER,
COURSE-DESC,
NUM-CREDITS,
GRADE
1NF to 2NF
2NF
STUDENT-NUMBER
STUDENT-NAME
TOTAL-CREDITS
GPA
ADVISOR-NUMBER
ADVISOR-NAME
COURSE-NUMBER
COURSE-DESC
NUM-CREDITS
STUDENT-NUMBER
COURSE-NUMBER
GRADE
11
A Normalization Example

You would create a new table for each field and
combination of fields in the primary key



STUDENT (STUDENT-NUMBER, STUDENT-NAME,
TOTAL-CREDITS, GPA, ADVISOR-NUMBER, ADVISORNAME)
COURSE (COURSE-NUMBER, COURSE-DESC, NUMCREDITS)
GRADE (STUDENT-NUMBER, COURSE-NUMBER,
GRADE)
12
A Normalization Example
STUDENT, COURSE, and GRADE tables in 2NF. Notice that all
fields are functionally dependent on the entire primary key of
their respective tables. [1]
13
A Normalization Example

3NF


Remove any transitive dependencies
No attribute dependent on a nonkey attribute



The COURSE and GREADE are in 3NF
STUDENT is not in 3NF, because the ADVISOR-NAME field
depends on the ADVISOR-NUMBER field, which is not part of
the STUDENT primary key
To convert STUDENT to 3NF, you remove the ADVISORNAME field from the STUDENT table and place it into a table
with ADVISOR-NUMBER as the primary key
14
A Normalization Example
Is this attribute dependent on
any other non-key attribute(s)?
2NF
STUDENT-NUMBER
STUDENT-NAME
TOTAL-CREDITS
GPA
ADVISOR-NUMBER
ADVISOR-NAME
COURSE-NUMBER
COURSE-DESC
NUM-CREDITS
STUDENT-NUMBER
COURSE-NUMBER
GRADE
3NF
STUDENT-NUMBER
STUDENT-NAME
TOTAL-CREDITS
GPA
ADVISOR-NUMBER
ADVISOR-NUMBER
ADVISOR-NAME
COURSE-NUMBER
COURSE-DESC
NUM-CREDITS
STUDENT-NUMBER
COURSE-NUMBER
GRADE
15
A Normalization Example
3NF
STUDENT-NUMBER
STUDENT-NAME
TOTAL-CREDITS
GPA
ADVISOR-NUMBER
Table Names
STUDENT
ADVISOR
ADVISOR-NUMBER
ADVISOR-NAME
COURSE-NUMBER
COURSE-DESC
NUM-CREDITS
STUDENT-NUMBER
COURSE-NUMBER
GRADE
COURSE
GRADE
16
A Normalization Example

3NF

The final 3NF design is
STUDENT (STUDENT-NUMBER, STUDENT-NAME,
TOTAL-CREDITS, GPA, ADVISOR-NUMBER)
 ADVISOR (ADVISOR-NUMBER, ADVISOR-NAME)
 COURSE (COURSE-NUMBER, COURSE-DESC, NUMCREDITS)
 GRADE (STUDENT-NUMBER, COURSE-NUMBER,
GRADE)

17
A Normalization Example
ADVISOR
ADVISES
STUDENT
RECEIVES
is on
COURSE
SHOWS
GRADE
Associative entity
The ERD for STUDENT, ADVISOR, and COURSE after normalization
18
A Normalization Example





Compare between the ERD before normalization and
after
After normalization we have four entitles: STUDENT,
ADVISOR, COURSE, and GRADE, which is an associative
entity
You can see that (M:N) relationship between STUDENT
and COURSE has been converted into two 1:M
relationships
One relationship between STUDENT and GRADE and the
other relationship between COURSE and GRADE
You should know that normal forms beyond 3NF exist,
but they rarely are used in business-oriented systems
19
Sequence Summary

1NF




2NF



All key attributes defined
No repeating groups in a table
All attributes dependent on a primary key
No attribute dependent on a portion of a primary key
Attributes may be functionally dependent on nonkey
attributes
3NF


Remove any transitive dependencies
No attribute dependent on a nonkey attribute
20
Sequence Summary

In this Sequence we have
 Explained the three steps of data
normalization through an example
21
Reference
[1] System Analysis and Design, Sixth
Edition
Authors: Gary B. Shelly, Thomas J.
Cashman and Harry J. Rosenblatt
Publisher: SHELLY CASHMAN SEWIES.
22