Database Reference
In-Depth Information
CHAPTER 8
RELATIONAL DATA MODEL
FUNDAMENTALS
CHAPTER OBJECTIVES
•
Understand how the relational model is a superior conventional data model
•
Study the components of the relational data model in detail
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Review the significance of data integrity and how this model provides proper
constraints
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Learn about data manipulation in the relational model and examine generic
languages
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Survey two common methods for relational model design
In Chapter 1, you had a very brief introduction to the relational data model. Before
the introduction of this data model, databases were developed based on the hier-
archical model first and then based on the network model. We also mentioned that
although these two models overcame most of the limitations of earlier file-oriented
data systems, a few drawbacks still remained. However, a landmark paper written
by Dr. E. F. Codd in 1970 completely changed the database scene. People began to
view data and databases in a different way. The era of relational database systems
started, and organization after organization began to adopt the new, superior model.
In the previous chapters, you have been studying semantic data modeling. You
went through the details of two methods for creating a semantic data model—
object-based data modeling and entity-relationship data modeling techniques. A
semantic data model represents the true meaning of the information requirements
of an organization. As explained in Chapter 5, a conventional model portrays how
data in the database are to be perceived. As mentioned before, the hierarchical,
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