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4 - Relational Data Model and Relational Database...

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Relational Data Model and Relational Database Constraints (Lecture Session-4) Chapter 5 Wed, January 27, 2010 1 DLPD, BITS-Pilani. Prepared by Dr.R. Gururaj, Asst.Professor of CS
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Wed, January 27, 2010 DLPD, BITS-Pilani. Prepared by Dr.R. Gururaj, Asst.Professor of CS 2 Contents 1.What is Relational model 2.Characteristics 3.Relational constrains 4.Representation of schemas
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Relational Model It is a representational data model. Using this representational (or implementation) model we represent a database as collection of relations . The notion of relation here is different from the notion of relationship used in ER modeling. A relation here is thought of as a table of values. Each row in the table represents a collection of related data. Each row contains facts about some entity of some entity-set. Wed, January 27, 2010 3 DLPD, BITS-Pilani. Prepared by Dr.R. Gururaj, Asst.Professor of CS
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Entities of each type/set are stored as rows in a single relation. Hence in general, a relation corresponds to a single entity. In some cases a relationship between two entities can have some specific attributes which can be captured in a relation (table).
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