Aggregation is an important concept in database design where composite objects can be modelled during the design of database applications. Therefore, preserving the aggregation concept in database implementation is essential. In this paper, we propose models for implementation of aggregation in an Object-Relational Database Management System (ORDBMS) through the use of index clusters and nested tables. ORDBMS is a commercial Relational Database Management Systems (RDBMS), like Oracle, which support some object-oriented concepts.
Aggregation represents abstract entities by allowing relationship between relationships. As you work with ER Diagrams you will come across the need for certain type of entities that are overlapping. For example, an 'Employee' 'works-on' a 'branch'. An 'Employee' 'manages' some tasks. The 'Works-on' entity here can be abstracted via the use ofaggregation. This is represented in a ER diagram by a diamond shape.
Aggregation represents abstract entities by allowing relationship between relationships. As you work with ER Diagrams you will come across the need for certain type of entities that are overlapping. For example, an 'Employee' 'works-on' a 'branch'. An 'Employee' 'manages' some tasks. The 'Works-on' entity here can be abstracted via the use ofaggregation. This is represented in a ER diagram by a diamond shape.
