Certain Conjunctive Query Answering in SQL

  • Alexandre Decan
  • Fabian Pijcke
  • Jef Wijsen
Part of the Lecture Notes in Computer Science book series (LNCS, volume 7520)


An uncertain database db is defined as a database in which distinct tuples of the same relation can agree on their primary key. A repair (or possible world) of db is then obtained by selecting a maximal number of tuples without ever selecting two distinct tuples of the same relation that agree on their primary key. Given a query Q on db, the certain answer is the intersection of the answers to Q on all repairs. Recently, a syntactic characterization was obtained of the class of acyclic self-join-free conjunctive queries for which certain answers are definable by a first-order formula, called certain first-order rewriting [15]. In this article, we investigate the nesting and alternation of quantifiers in certain first-order rewritings, and propose two syntactic simplification techniques. We then experimentally verify whether these syntactic simplifications result in lower execution times on real-life SQL databases.


Conjunctive Query Query Answering Probabilistic Database Attack Graph Nest Depth 
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 2012

Authors and Affiliations

  • Alexandre Decan
    • 1
  • Fabian Pijcke
    • 1
  • Jef Wijsen
    • 1
  1. 1.Université de MonsMonsBelgium

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