Optimization of nested queries in a complex object model

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

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

    14 Citations (Scopus)
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    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
    ISBN (Print)3-540-57818-8
    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
    ISSN (Print)0302-9743
    ISSN (Electronic)1611-3349


    Conference4th International Conference on Extending Database Technology, EDBT 1994
    Abbreviated titleEDBT
    Country/TerritoryUnited Kingdom


    • METIS-118956
    • IR-96073


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