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Positive Relational Algebra

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  • First Online:
Encyclopedia of Database Systems

  • 44 Accesses

Synonyms

SPJRU-algebra; SPCU-algebra

Definition

Positive relational algebra is the fragment of relational algebra which excludes the difference operator. Relational algebra queries are expressions defining mappings from database instances of an input database schema to an output relation. In particular a positive relational algebra query over a database schema Ï„ is one of the following expressions, each one with an associated set of attributes:

  • A constant relation over a set of attributes U is a positive relational algebra query with associated set of attributes U.

  • If R(U) is a relation schema in Ï„, the relation symbol R is a positive relational algebra query with associated set of attributes U.

  • If Q and Q′ are positive relational algebra queries with sets of attributes U and U′, respectively, the following are positive relational algebra queries:

    • The selection σ A=B (Q) or σ A=c (Q), with set of attributes U, where A and B are attributes in U, and c is a constant value

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Recommended Reading

  1. Abiteboul S, Hull R, Vianu V. Foundations of databases. Reading: Addison-Wesley; 1995.

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Author information

Authors and Affiliations

  1. IRIF, Paris Diderot University, Paris, France

    Cristina Sirangelo

Authors
  1. Cristina Sirangelo
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Corresponding author

Correspondence to Cristina Sirangelo .

Editor information

Editors and Affiliations

  1. Georgia Institute of Technology College of Computing, Atlanta, Georgia, USA

    Ling Liu

  2. University of Waterloo School of Computer Science, Waterloo, Ontario, Canada

    M. Tamer Özsu

Section Editor information

  1. School of Informatics, University of Edinburgh, Crichton Street, EH8 9LE, Edinburgh, Scotland, UK

    Leonid Libkin

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© 2017 Springer Science+Business Media LLC

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Sirangelo, C. (2017). Positive Relational Algebra. In: Liu, L., Özsu, M. (eds) Encyclopedia of Database Systems. Springer, New York, NY. https://doi.org/10.1007/978-1-4899-7993-3_1251-2

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  • DOI: https://doi.org/10.1007/978-1-4899-7993-3_1251-2

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  • Publisher Name: Springer, New York, NY

  • Print ISBN: 978-1-4899-7993-3

  • Online ISBN: 978-1-4899-7993-3

  • eBook Packages: Springer Reference Computer SciencesReference Module Computer Science and Engineering

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