Optimization of nested queries in a complex object model

H.J. Steenhagen, Hennie J. Steenhagen, Peter M.G. Apers, Henk Blanken

    Research output: Chapter in Book/Report/Conference proceedingConference contributionAcademicpeer-review

    13 Citations (Scopus)
    79 Downloads (Pure)

    Abstract

    Transformation of nested SQL queries into join queries is advantageous because a nested SQL query can be looked upon as a nested-loop join, which is just one of the several join implementations that may be available in a relational DBMS. In join queries, dangling (unmatched) operand tuples are lost, which causes a problem in transforming nested queries having the aggregate function COUNT between query blocks-a problem that has become well-known as the COUNT bug. In the relational context, the outerjoin has been employed to solve the COUNT bug. In complex object models supporting an SQL-like query language, transformation of nested queries into join queries is an important optimization issue as well. The COUNT bug turns out to be a special case of a general problem being revealed in a complex object model. To solve the more general problem, we introduce the nest join operator, which is a generalization of the outerjoin for complex objects.
    Original languageEnglish
    Title of host publicationAdvances in database technology - EDBT '94
    EditorsMatthias Jarke, Janis Bubenko, Keith Jeffery
    Place of PublicationBerlin
    PublisherSpringer
    Pages337-350
    ISBN (Print)3-540-57818-8
    DOIs
    Publication statusPublished - 28 Mar 1994
    Event4th International Conference on Extending Database Technology, EDBT 1994 - Cambridge, United Kingdom
    Duration: 28 Mar 199431 Mar 1994
    Conference number: 4

    Publication series

    NameLecture notes in computer science
    PublisherSpringer
    Volume779
    ISSN (Print)0302-9743
    ISSN (Electronic)1611-3349

    Conference

    Conference4th International Conference on Extending Database Technology, EDBT 1994
    Abbreviated titleEDBT
    CountryUnited Kingdom
    CityCambridge
    Period28/03/9431/03/94

    Keywords

    • METIS-118956
    • IR-96073

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  • Cite this

    Steenhagen, H. J., Steenhagen, H. J., Apers, P. M. G., & Blanken, H. (1994). Optimization of nested queries in a complex object model. In M. Jarke, J. Bubenko, & K. Jeffery (Eds.), Advances in database technology - EDBT '94 (pp. 337-350). (Lecture notes in computer science; Vol. 779). Berlin: Springer. https://doi.org/10.1007/3-540-57818-8_62