Relational theory of queries

摘要

In this paper a new presentation of the relational theory of queries will be given. Both the relational algebra and the (domain) relational calculus will be systematically derived from first-order logic. The connections between logic, algebra and calculus will become extremely simple: e.g. the relational algebra will be isomorphic with a subset of relational calculus. Also some theoretical results about the completeness of the relational query languages will be presented. Both the relational calculus and the relational algebra will be extended to contain aggregate functions.