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Aggregation
A number of functions that combine records from one or more tables to produce potentially useful information. A relation, such as CONSISTS OF or CONTAINS, between types that defines the composition of a type from other types.
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A primary key from another table used to cross-link or express relationships between the contents of two tables. A primary key of one file (relation) that appears in another file (relation).
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The language mechanism that allows the definition of a class to include the attributes and methods for another more general class. Inheritance is an implementation construct for the specialization relation. The general class is the superclass and the specific class is the subclass in the inheritance relation. Inheritance is a relation between classes that enables the reuse of code and the definition of generalized interface to one or more subclasses.
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A database that consists of tables that contain a set of related records. In a relational database, data is organized in twodimensional tables or relations.
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A relation the user creates to eliminate a manytomany relationship. Also called a composite relation.
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The number of attributes or columns of a relation.
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