Synonyms
Object query language
Definition
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
Bancilhon F, Delobel C, Kanellakis PC. Building an object-oriented database system, the story of O2. Los Altos: Morgan Kaufmann; 1992.
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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.
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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.
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Gray, P.M.D. (2018). OQL. In: Liu, L., Özsu, M.T. (eds) Encyclopedia of Database Systems. Springer, New York, NY. https://doi.org/10.1007/978-1-4614-8265-9_1118
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