Acta Informatica

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

Testing bag-containment of conjunctive queries

  • Nieves R. Brisaboa
  • Héctor J. Hernández


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.


Semantic Relation Conjunctive Query Canonical Database 
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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: 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: US

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