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Cluster index Vs IOT

Discussion in 'SQL PL/SQL' started by prashant, Jan 16, 2009.

  1. prashant

    prashant Forum Advisor

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    Hi,

    Can anyone explain me the difference between clustered index and an Index Organised Table?

    Thanks & Regards,
    Prashant
     
  2. zargon

    zargon Community Moderator Forum Guru

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    You're comparing Sybase/SQL Server to Oracle with that question.

    Sybase/SQL Server offers a clustered index. In that type of index the leaf nodes are the table data, and as such the table data is ordered by index key. You cannot physically separate a clustered index from the table.

    Oracle offers the IOT, which is basically the same thing: it is a table which uses a b-tree index structure so, again, the leaf nodes of the index are the actual table data. This is a single object, not two as in Sybase/SQL Server. You can create additional indexes against an IOT in Oracle releases 9i and later.

    In either case using such a configuration is not recommended for tables which are subject to heavy transactional activity (inserts/deletes).
     
  3. prashant

    prashant Forum Advisor

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    Thank you Zargon for your Reply. I got confused. Now its sorted out.

    Also one doubt. I Oracle do we call indexes on clustered tables as "Clustered Indexes"?

    Thanks.

    Regards,
    Prashant