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This database contains information about employees, departments and projects. Ba (entity) teaches (relationship) the Database Systems course (entity).įor the rest of this chapter, we will use a sample database called the COMPANY database to illustrate the concepts of the ER model. Here is an example of how these two concepts might be combined in an ER data model: Prof. Relationships, defined as the associations or interactions between entities.
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Entities , defined as tables that hold specific information (data).ER models are readily translated to relations. ER models, also called an ER schema, are represented by ER diagrams. It is well suited to data modelling for use with databases because it is fairly abstract and is easy to discuss and explain. The entity relationship (ER) data model has existed for over 35 years.
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Chapter 8 The Entity Relationship Data Model