Encyclopedia of Database Systems

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


  • Peter M. D. GrayEmail author
Reference work entry
DOI: https://doi.org/10.1007/978-1-4614-8265-9_1118


Object query language


OQL was developed to play the role of SQL for Object-Oriented Databases, especially those adhering to the ODMG Standard [4] where the language is defined. Unlike SQL, OQL is a functional language, and its operators can be composed to an arbitrary level of nesting within a query provided the query remains type-correct. Fegaras and Maier [8] have shown how OQL expressions have a direct translation into monoid Comprehensions.

Optimisation techniques for OQL that exploit its inherent functional nature are discussed in [5, 6, 8]. OQL has been influential in the development of the SQL3 standard and also the functional core of the XQuery language for XML. Thus optimisation techniques developed for OQL are also applicable to these languages.

Key Points

The fundamental modelling concept of object identifiersfor entity instances was accepted into the database mainstream in the late 1980s, and the move to using SQL-like syntax for querying such data...

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Recommended Reading

  1. 1.
    Bancilhon F, Delobel C, Kanellakis PC. Building an object-oriented database system, the story of O2. Los Altos: Morgan Kaufmann; 1992.Google Scholar
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    Beech D. A foundation of evolution from relational to object databases. In: Advances in Database Technology. Proceedings of the 1st International Conference on Extending Database Technology; 1988. p. 251–70.Google Scholar
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    Buneman P, Libkin L, Suciu D, Tannen V, Wong L. Comprehension syntax. ACM SIGMOD Rec. 1994;23(1):87–96.CrossRefGoogle Scholar
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    Cattell RGG, editor. The object data standard: ODMG 3.0. Los Altos: Morgan Kaufmann; 2000.Google Scholar
  5. 5.
    Cluet S, Delobel C. A general framework for the optimization of object-oriented queries. In: Proceedings of the ACM SIGMOD International Conference on Management of Data; 1992. p. 383–92.Google Scholar
  6. 6.
    Fegaras L. Query unnesting in object-oriented databases. In: Proceedings of the ACM SIGMOD International Conference on Management of Data; 1998. p. 49–60.Google Scholar
  7. 7.
    Fegaras L. Query processing and optimization in λ-DB, Chapter 13. In: Gray PMD, Kerschberg L, King PJH, Poulovassilis A, editors. The functional approach to data management. Berlin: Springer; 2004.Google Scholar
  8. 8.
    Fegaras L, Maier D. Towards an effective calculus for Object Query Languages. In: Proceedings of the ACM SIGMOD International Conference on Management of Data; 1995. p. 47–58.CrossRefGoogle Scholar

Copyright information

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

Authors and Affiliations

  1. 1.University of AberdeenAberdeenUK

Section editors and affiliations

  • Tore Risch
    • 1
  1. 1.Department of Information TechnologyUppsala UniversityUppsalaSweden