Encyclopedia of Database Systems

2018 Edition
| Editors: Ling Liu, M. Tamer Özsu

Top-k Queries

  • Ihab F. Ilyas
Reference work entry
DOI: https://doi.org/10.1007/978-1-4614-8265-9_3843

Synonyms

Ranking queries; Top-n queries

Definition

A top-k query retrieves up to k query answers with the highest (lowest) score according to some scoring function f, where ties are resolved arbitrarily. Without loss of generality, we assume that we retrieve the results with highest scores. In other words, top-k queries return a subset of the query answers S ⊂ Q such that
$$ \left|S\right|{\le} k\bigwedge \forall t{\in} S\nexists r{\in} \left(Q{-}S\right)\bigwedge F(r){>}F(t) $$
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Copyright information

© Springer Science+Business Media, LLC, part of Springer Nature 2018

Authors and Affiliations

  1. 1.Cheriton School of Computer Science, University of WaterlooWaterlooCanada

Section editors and affiliations

  • Ihab F. Ilyas
    • 1
  1. 1.Cheriton School of Computer ScienceUniversity of WaterlooWaterlooCanada