March 2022
Intermediate to advanced
682 pages
22h 58m
English
Content preview from Databases Illuminated, 4th Edition
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9.9 Converting an Extended Entity-Relationship (EER) Diagram to an OR Database Model
The OR model provides much more flexibility in mapping an EER diagram than does the strictly relational model. As illustrated in our examples, we can make use of new data types, user-defined structured types, inheritance, and reference types in creating our tables. We modify the EER-to-relational mapping algorithm (presented in Chapter 4, Section 4.8.2) to incorporate the extensions.
For entity sets and relationships that are not part of generalizations or unions, the mapping can proceed in a manner similar to the relational model. Entity sets can be mapped to tables, creating a type and then creating an object table of that type. For composite attributes, we ...
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