Class Agenda (11/06, 11/08)
Review HW #8 answers
Present normalization process

Enhance conceptual knowledge of database design.

Improve practical skills of database design.
Approach this week

Identify and define vocabulary for normalization.

Discuss the characteristics of the three normal forms and the
characteristics of a data model in third normal form.

Use the normalization process to do the same database
design as done intuitively last week.

Compare results.
1
What is normalization?
Normalization is a formal, process-oriented
approach to data modeling.
Normalization is the process of:

examining groups of data attributes;

splitting them into appropriate entities;

identifying the relationships between the
entities; and

identifying appropriate primary and foreign
keys.
2
Same old/same old
Normalization should sound like what you have
already done during database design.
The ultimate goals of design have not changed;
we are just going to go about it in a slightly
different way.
3
Database Normalization
What will you know about database normalization?

Define normalization.

Know the vocabulary of normalization.

Understand the process of normalization.

Better understand the characteristics of an effective database
design.
What will you be able to do?

Be able to identify the characteristics of each normal form.

Be able to tell whether or not a data model is in third normal
form.

Potentially be able to use normalization to assist you in the design
of a database.
4
Normalization process
Some refer to this as the “bottom-up” form of
database design.
Contrast with the more intuitive “top-down”
approach we have been using.
The results from the normalization process are
stable, flexible entities. The results from the
intuitive approach should be the same.
5
Two methods of applying normalization
1.
Use it to help in designing a database.

Normalization starts with a single entity.

Normalization breaks that entity into a series of additional entities.

More entities are discovered and named during the process.

Entities are linked during the process.
2.
Use it to validate the design of a database.

Identify entities from the meaning of the data.

Create conceptual and logical data models.

Apply the rules of normalization to ensure a stable, non-redundant
design.
6
Vocabulary for normalization
A “functional dependency" is a relationship
between attributes in which one attribute or group
of attributes determines the value of another.
A “determinant” is an attribute or group of
attributes that, once known, can determine the
value of another attribute.
7
Examples of functional
dependencies and determinants
A social security number determines your name and address.
SSN  name, address.
A vehicle id number determines the make and model of a car.
VIN  make, model.
Name and address are “functionally dependent” on SSN.
SSN “determines” name and address.
Functional dependency diagram format:

CourseID  CourseName, CourseDescription, CourseCredits

ZipCode  City, State

PatientID, TreatmentDateTime  TestResults
Normalization process
Normalization is accomplished in stages.
A
“normal form” is a state (level of completeness) of
a data model.
Unnormalized data:
A data model that has not
been normalized. It contains repeating groups and
is not a stable model.
Unnormalized data is essentially one entity.
The
system under analysis is categorized as a single
entity.
9
Steps/forms/phases in
Normalization
First normal form: Remove repeating groups.
Second normal form: Remove partial functional
dependencies.
Third normal form:
Remove transitive
dependences
10
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Semester
Unnormalized data for
grade report exercise
Year
Student Name
Student Address
Student City
Student State
Student Zip Code
What attributes might be
needed that aren’t visible on
the grade report?
Student ID
Student College
Student Major
Student Minor
Student Year
Course ID
Course Title
Course Instructor
Course Credits
Grade
Group all attributes in
one “big” entity.
Identify a primary key for
the entity.
Maybe studentID for this
one.
First Normal Form
First normal form:

Remove repeating groups.
A repeating group is an attribute or group of attributes that can
have more than one value for an instance of an entity. If it is a single
attribute, we have been calling it a “multi-valued” attribute.
To get a data model into first normal form:

Identify repeating groups and place them as separate entities in the
model.

Identify a primary key for the repeating group. The key may be
concatenated.

Create the relationships between entities.

Divide m:n relationships with appropriate intersection entities.
12
Second Normal Form
Second normal form:
dependencies.
Remove partial functional
A partial functional dependency is a situation in which one
or more non-key attributes are functionally dependent on
part, but not all, of the primary key.

Partial functional dependencies occur only with concatenated keys.
Examples of partial functional dependencies:


PatientID, TreatmentDateTime  PatName, TstResults, TrtID, LocID
CourseID, StudentID  CourseTitle, Grade
Which entities developed during the transition to first
normal form for the grade report have concatenated keys?
13
Third normal form
Third normal form:

Remove transitive dependencies.
A transitive dependency occurs when a non-key attribute is
functionally dependent on one or more non-key attributes.
Third normal form examines entities with single primary
keys and removes the “floating” or transitive dependencies.
It may be possible to have attributes that are determined
by other attributes, rather than by the primary key. They
must be removed into entities with appropriate primary
keys.
Example of partial functional dependency:

PatID, TrtDateTime  TstResults, TrtType, TrtDescription, LocName,
TrtID, LocID
14
Summary of normalization process
Examine and evaluate the logical data model for
effectiveness.

Find the repeating groups and put the model into first normal
form. Identify primary key fields for any new entities. Relate
entities with foreign keys.

Find the functional dependencies. Identify the partial
functional dependencies and put the model into second
normal form. Identify primary key fields for any new entities.
Relate entities with foreign keys.

Find the transitive dependencies and put the model into third
normal form. Identify primary key fields for any new entities.
Relate entities with foreign keys.
15
Goal of normalization
A set of entities where each
attribute in each entity is
dependent on the primary key,
the whole primary key, and
nothing but the primary key!!
16