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Thread: full table scan

  1. #1
    Join Date
    Mar 2001
    south africa

    full table scan

    I have query when i run explain plan , i see several full table scan going on.there are indexes on these tables.how to reduce full table scan on these and use some indexes etc?

  2. #2
    Join Date
    Sep 2002
    why are you assuming a full table scan is bad

  3. #3
    Join Date
    Mar 2004
    Oracle db would decide whether it needs full table scan or use indexes based on certain set parameters.
    "What is past is PROLOGUE"

  4. #4
    Join Date
    Aug 2002
    Colorado Springs
    .. and based on statistics on the objects etc..

    Welll a full-scan is neither good nor bad, it is just a thing. You can promote index usage in a number of ways, and for a single query the simplest may be to just use hints to promote index usage.

    However, take the trouble to measure and document performance with and without the indexes being used, and keep an open mind on whether you ought to be using them or not. If you can conclude that there are clear benefits to using the indexes then you can look to see why the optimizer is not doing so. It may have bad information about the tables, the indexes, the data, the system ... but the first step is to see whether it is right or wrong in the first place.
    David Aldridge,
    "The Oracle Sponge"

    Senior Manager, Business Intelligence Development
    XM Satellite Radio
    Washington, DC

    Oracle ACE

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