Chapter3 - 3 Chapter 3 The Relational Database Model...

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3 1 Chapter 3 The Relational Database Model Database Systems: Design, Implementation, and Management, Sixth Edition, Rob and Coronel
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3 2 In this chapter, you will learn: That the relational database model takes a logical view of data That the relational model’s basic components are entities, attributes, and relationships among entities How entities and their attributes are organized into tables
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3 3 In this chapter, you will learn ( continued ): About relational database operators, the data dictionary, and the system catalog How data redundancy is handled in the relational database model Why indexing is important
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3 4 A Logical View of Data Relational model Enables us to view data logically rather than physically Reminds us of simpler file concept of data storage Table Has advantages of structural and data independence Resembles a file from conceptual point of view Easier to understand than its hierarchical and network database predecessors
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3 5 Tables and Their Characteristics Table : two-dimensional structure composed of rows and columns Contains group of related entities an entity set Terms entity set and table are often used interchangeably
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3 6 Tables and Their Characteristics ( continued ) Table also called a relation because the relational model’s creator, Codd, used the term relation as a synonym for table Think of a table as a persistent relation : A relation whose contents can be permanently saved for future use
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3 7 Characteristics of a Relational Table 1. A table is perceived as a tow-dimensional structure composed of rows and columns. 2. Each table row (tuple) represents a single entity occurrence
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Chapter3 - 3 Chapter 3 The Relational Database Model...

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