SQL Server Performance

What is covering index?

Discussion in 'Performance Tuning for DBAs' started by sramesh, Sep 14, 2006.

  1. sramesh New Member

    Hi,
    Is covering index perform fast?
    Plase give me some example

    Thanks
    S. Ramesh
  2. dineshasanka Moderator

  3. sramesh New Member

    Covering Index = Composite Index?

    Thanks
    S. Ramesh
  4. satya Moderator

    A composite index is an index that is made up of more than one column. In some cases, a composite index is also a covering index. (as referred by Dinesh's link).

    IMHO, composite indexes (with the exception of covering indexes) should be avoided. This is because composite indexes tend to be wide, which means that the index will be larger, requiring more disk I/O to read it, hurting performance.


    Satya SKJ
    Microsoft SQL Server MVP
    Contributing Editor & Forums Moderator
    http://www.SQL-Server-Performance.Com
    This posting is provided AS IS with no rights for the sake of knowledge sharing.
  5. sramesh New Member

    ok
    tell me how to create a covering index?

    Thanks
    S. Ramesh
  6. FrankKalis Moderator


    CREATE INDEX ... ON Table(all involved column go here)


    --
    Frank Kalis
    Moderator
    Microsoft SQL Server MVP
    Webmaster:http://www.insidesql.de
  7. satya Moderator

    Lookup at Books online too for code examples.

    quote:Originally posted by sramesh

    ok
    tell me how to create a covering index?

    Thanks
    S. Ramesh

    Satya SKJ
    Microsoft SQL Server MVP
    Contributing Editor & Forums Moderator
    http://www.SQL-Server-Performance.Com
    This posting is provided AS IS with no rights for the sake of knowledge sharing.

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