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RowGUIDCol

  • March 22, 2006 at 5:33 am

    #93672

     

    What is the use of RowGUIDCol in SQl 2000?

    Regards,

    ManoKarnan

     

  • March 22, 2006 at 5:56 am

    #628058

    Consider it as an extention to "Identity"

    from books online (BOL)

    If an application must generate an identifier column that is unique across the entire database, or every database on every networked computer in the world, use the ROWGUIDCOL property, the uniqueidentifier data type, and the NEWID function.

    When you use the ROWGUIDCOL property to define a globally unique identifier column, consider that:

    • A table can have only one ROWGUIDCOL column, and that column must be defined using the uniqueidentifier data type.

    • SQL Server does not automatically generate values for the column. To insert a globally unique value, create a DEFAULT definition on the column that uses the NEWID function to generate a globally unique value.

    • The column can be referenced in a select list by using the ROWGUIDCOL keyword after the ROWGUIDCOL property is set. This is similar to the way an IDENTITY column can be referenced using the IDENTITYCOL keyword.

    • The OBJECTPROPERTY function can be used to determine if a table has a ROWGUIDCOL column, and the COLUMNPROPERTY function can be used to determine the name of the ROWGUIDCOL column.

    • Because the ROWGUIDCOL property does not enforce uniqueness, the UNIQUE constraint should be used to ensure that unique values are inserted into the ROWGUIDCOL column.

    Note  If an identifier column exists for a table with frequent deletions, gaps can occur between identity values; deleted identity values are not reused. To avoid such gaps, do not use the IDENTITY property. Instead, you can create a trigger that determines a new identifier value, based on existing values in the identifier column, as rows are inserted.

    Johan

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