Difference between Unique Clustered Index & Non Unique Clustered Index

  • Thanks Gail and Allen for this learning discussion amd information sharing.

    Thanks a ton. Bye

    Ankur

  • GilaMonster (7/27/2009)


    allen davidson (7/27/2009)


    I think my reply should have been along the lines of...

    clustered indexes affect placement on disk

    Not necessarily true either. Think about fragmented indexes, fragmented file system, striping, etc. If you haven't read that article I linked, please do.

    The clustered index may affect the placement of pages within the data file, but it's not the only thing that does. That's why I definitely prefer to talk about the logical ordering rather than physical because so many other things can and do affect the physical location of the pages on disk.

    May I encourage everyone to occassionally do a physical defragment of their disks occassionally, maybe during a scheduled maintenance window after any patching is done but before you start the services again. Yes, the database may be technically 1 file, but if you had 2000+ fragments like I did, sometimes that does a world of good.

    Gaby________________________________________________________________"In theory, theory and practice are the same. In practice, they are not." - Albert Einstein

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