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note4-ermapping - foreign key The entity at N side includes...

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1 CSc 134 Database Management and File  Organization 4. Relational Database Design by  ER-to-Relational Mapping Ying Jin Computer Science Department California state University, Sacramento
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2 ER to Relational Mapping ER is a conceptual model Map conceptual model to  representational /implementation model
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3 (Strong) Entity Create a relation for the entity Include all the simple attribute and simple  composite attributes of a composite attribute
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4 Weak Entity The primary key of an weak entity is the  combination of the primary key of the  owner(s) and the partial key of the weak  entity.
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5 1:1 Relationship  Chose one entity to include the primary  key of the other entity as  foreign key . Include simple attributes of the relation It is better to choose an entity type with  total participation. 
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6 1:N Relationship The entity at N side includes the  primary key of the entity at 1 side as 
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Unformatted text preview: foreign key. The entity at N side includes simple attributes of the relation 7 1:N Recursive Relationship The entity includes the primary key of itself as foreign key to represent the recursion 8 M:N Relationship Create a new relation for the relationship Include the primary keys of the two entities as foreign keys. The combination of two foreign keys as the primary key of the new relation. 9 Multivalued Attributes Create a new relation R for a multivalued attribute A (of entity E). R includes an attribute corresponding to A and the primary key of E as the foreign key. The combination of A and this foreign key as the primary key of R . 10 The note is based on the textbook: R. Elmaseri and S. Navathe, Fundamentals of Database Systems , 5th Edition, Addison-Wesley....
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