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Unique Clusered Index

  • January 13, 2005 at 10:36 am

    #87267

    Hi All,

    SQL Server 2000 allows me to create a Unique Clusered Index or a Unique Clusered Constraint.

    What is the difference?

    Thanks,

    -Kevin

  • January 13, 2005 at 12:53 pm

    #537362

    An index is sorted, a constraint is not.  Both will have statistics.  Index will be used for data lookup.

    Tom

  • January 13, 2005 at 1:08 pm

    #537368

    You might want to read SQL Server's Online Help on both topics or search the fora here.

    --
    Frank Kalis
    Microsoft SQL Server MVP
    Webmaster: http://www.insidesql.org/blogs
    My blog: http://www.insidesql.org/blogs/frankkalis/[/url]

  • January 13, 2005 at 1:39 pm

    #537374

    The BOL states that "SQL Server automatically creates a UNIQUE index to enforce the uniqueness requirement of the UNIQUE constraint."

    So if a clustered unique index is implicitly created along with the constraint I still am confused as to what the effective difference would be.

  • January 21, 2005 at 2:51 am

    #538459

    Hi Kevin

    As I understand it, a constraint has to do with inputting data into the table. If the constraint is unique, you would not be able to insert a record that would violate the condition. But the constraint is not used for data retrieval.

    An index, on the other hand, is used for data retrieval. A unique index is, I think, an index with a constraint.

    Schalk

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