We define the class of conjunctive queries in relational data bases, and the generalized join
operator on relations. The generalized join plays an important part in answering conjunctive …

The concept of a “reasonable” query in a relational data base is investigated. We provide an
abstract characterization of the class of queries which are computable, and define the …

Query languages for relational databases have received considerable attention. In 1972
Codd [Cod72] showed that two natural mathematical languages for queries—one algebraic …

We consider the task of enumerating and counting answers to k-ary conjunctive queries
against relational databases that may be updated by inserting or deleting tuples. We exhibit …

Abstract 1 Introduction (! orajtlnrtinr-gaerll rontainment is recognized as a fundamonlnl
probhi in database query evaluation and optimization, At the mtx bitnc, constraint satisfaction …

Answering queries in a relational database often requires that the natural join of two or more
relations be computed. However, the result of a join may not be what one expects. In this …

It is known that the expression complexity and combined complexity of query evaluation in
relational databases are in general exponentially higher than the data complexity of query …

This paper examines a number of programming primitives in query languages for relational
databases. The basic framework is a language based on relational algebra, whose …

We are interested in the theoretical foundations of the optimization of conjunctive regular
path queries (CRPQs). The basic problem here is deciding query containment both in the …

The nested relational model provides a better way to represent complex objects than the
(flat) relational model, by allowing relations to have relation-valued attributes. A recursive …