4.1. Conceptual Schemas
The collection of data objects a computer application needs is called its database. The predominant technology for storing and accessing a database is a relational database management system, or relational DBMS. It is therefore important to understand the capabilities of this technology and to know its terminology. Even if we don’t plan to use a relational DBMS ourselves, we can still learn a great deal.
The relational model of databases assumes that anything we want to represent can be modelled as a collection of relations. The assumption is valid because relations can represent predicates, and predicate calculus can represent any finite set of facts.
A relational database comprises one or more tables . The number of columns ...
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