Database Reference
In-Depth Information
6
DATABASE DESIGN 2: DESIGN
METHOD
CHAPTER
LEARNING OBJECTIVES
Discuss the general process and goals of database design
Define user views and explain their function
Define Database Design Language (DBDL) and use it to document database designs
Create an entity-relationship (E-R) diagram to visually represent a database design
Present a method for database design at the information level and view examples illustrating
this method
Explain the physical-level design process
Discuss top-down and bottom-up approaches to database design and examine the advantages
and disadvantages of both methods
Use a survey form to obtain information from users prior to beginning the database design
process
Review existing documents to obtain information prior to beginning the database design
Discuss special issues related to implementing one-to-one relationships and many-to-many
relationships involving more than two entities
Discuss entity subtypes and their relationships to nulls
Learn how to avoid potential problems when merging third normal form relations
Examine the entity-relationship model for representing and designing databases
INTRODUCTION
Now that you have learned how to identify and correct poor table designs, you will turn your attention to the design process
by determining the tables (relations) and columns (attributes) that make up the database. In addition, you will determine the
relationships between the various tables.
Most designers tackle database design using a two-step process. In the first step, the database designers design a
database that satisfies the organization's requirements as cleanly as possible. This step, which is called
information-level
design
, is completed
independently
of any particular DBMS that the organization will ultimately use. In the second step,
which is called the
, designers adapt the information-level design for the specific DBMS that the
organization will use. During the physical-level design, designers must consider the characteristics of the particular DBMS
that the organization will use.
After examining the information-level design process, you will explore the general database design method and view
examples illustrating this method. You will construct entity-relationship diagrams to represent the database design visually.
You will then learn about the physical-level design process. You will also compare top-down and bottom-up approaches to
database design.
You will explore special issues related to database design, including survey forms and their use in database design
and the way to obtain important information from existing documents. You will examine issues related to the implementation
of some special types of relationships. You will learn about entity subtypes and their relationship to nulls. You will examine
issues related to merging third normal form relations. Finally, you will learn about the entity-relationship model.
physical-level design
