lec04.366

lec04.366 - . . Winter 2008 CPE/CSC 366: Database Modeling,...

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. . Winter 2008 CPE/CSC 366: Database Modeling, Design and Implementation Alexander Dekhtyar . . From E-R Models to Relational Databases E-R Modeling Framework vs. Relational Database Model Entity-Relationship Models Entities: objects Attributes: individual features of objects Keys: means of unique identiFcation of objects Relationships: associations between objects Entity Sets: collections of objects Relationship Sets: collections of associations Constraints: restrictions on objects and associations Weak Entity Sets: entity sets w/o a key Relational Database Model Relatinal Table: 2D representation of data Table row: data about a single object Table column: one attribute Table schema: list of columns making a table Database schema: list of relational table schemas Primary key: unique identiFcation of rows in tables Foreign key: primary key of one table included in another table From E-R Models to Database Schemas Basic Translation Entity Sets are translated into relational tables with the same attributes and the same primary keys . Note: This applies only to strong entity sets . Relationship Sets are translated into relational tables which consist of the following attributes: Primary keys of all tables representing entity sets which participate in the relationship set. Must be declared as foreign keys . Any
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lec04.366 - . . Winter 2008 CPE/CSC 366: Database Modeling,...

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