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Acta Informatica

, Volume 34, Issue 7, pp 557–578 | Cite as

Testing bag-containment of conjunctive queries

  • Nieves R. Brisaboa
  • Héctor J. Hernández

Abstract.

Under the bag-theoretic semantics relations are bags of tuples, that is, a tuple may have any number of duplicates. Under this semantics, a conjunctive query \(Q\) is bag-contained in a conjunctive query \(Q^{\prime }\), denoted \( Q\leq _bQ^{\prime }\), if for all databases \({\cal D}\), \(Q({\cal D})\), the result of applying \(Q\) to \({\cal D}\), is a subbag of \( Q^{\prime }({\cal D)}\). It is not known whether testing \(Q\leq _bQ^{\prime }\) is decidable. In this paper we prove that \(Q\leq _bQ^{\prime }\) can be tested on a finite set of canonical databases built from the body of \(Q\). Using that result we give a procedure that decides the bag-containment problem of conjunctive queries in a large number of cases.

Keywords

Semantic Relation Conjunctive Query Canonical Database 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Springer-Verlag Berlin Heidelberg 1997

Authors and Affiliations

  • Nieves R. Brisaboa
    • 1
  • Héctor J. Hernández
    • 2
  1. 1. Departamento de Computación, Facultad de Informática, Universidad de A Coruña, E-15071 A Coruña, Spain (e-mail: cinbrisa@udc.es) ES
  2. 2. Laboratory for Logic, Databases, and Advanced Programming, Department of Computer Science, New Mexico State University, Las Cruces, NM 88003-8001, USA (e-mail: hector@cs.nmsu.edu) US

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