April 2013 Archive

Summary of The Entity-Relationship Data Model

The Entity/Relationship Model: In the E/R model we explain entity sets, relationships among entity sets, and attributes of entity sets and relationships. Members of entity sets are called entities.

The Relational Data Model

While the entity-relationship approach to data modeling that we discussed in "The Entity-Relationship Data Model" is a simple and suitable way to explain the structure of data,

Attributes / Schemas

Across the top of a relation we see attributes; in the following figure, the attributes are title, year, length, and filmType. Attributes of a relation serve as names for the columns of the

Tuples / Domains

The rows of a relation, other than the header row containing the attribute names, are called tuples. A tuple has one component for each attribute of the relation. For example, the first of the three

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