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Relational Database Design and Implementation, 3rd Edition by Jan L. Harrington

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Chapter 4. Entities and Relationships
In this chapter we look at the basis for all database systems: the relationships between elements in the database environment. The formal term for expressing data relationships to a DBMS is a data model. The relational data model, which you will learn about in this book, is just such a formal structure. However, the underlying relationships in a database are independent of the data model and therefore also independent of the DBMS you are using. Before you can design a database for any data model, you need to be able to identify data relationships.
Note: Most DBMSs support only one data model. Therefore, when you choose a DBMS, you are also choosing your data model.

Entities and Their Attributes

An entity is something ...

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