Databases Reference
In-Depth Information
CHAPTER
6
METHOD
LEARNING OBJECTIVES
Objectives
Discuss the general process and goals of database design
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Define user views and explain their function
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Define Database Design Language (DBDL) and use it to document database designs
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Create an entity-relationship (E-R) diagram to visually represent a database design
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Present a method for database design at the information level and view examples illustrating
this method
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Explain the physical-level design process
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Discuss top-down and bottom-up approaches to database design and examine the advan-
tages and disadvantages of both methods
●
Use a survey form to obtain information from users prior to beginning the database design
process
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Review existing documents to obtain information prior to beginning the database design
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Discuss special issues related to implementing one-to-one relationships and many-to-many
relationships involving more than two entities
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Discuss entity subtypes and their relationships to nulls
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Learn how to avoid potential problems when merging third normal form relations
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Examine the entity-relationship model for representing and designing databases
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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 is called
information-level design
, and it is completed
independently
of any particular DBMS that the organization will ultimately use. In the second step, which is called the
physical-level
design
, 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.
