It's a declaritive way for creating a UNIQUE index. By using constraints, the rules become part of the schema.

-Mike

>>Hmmm...interesting question. According to the BOL:
>>
>>"If IGNORE_DUP_KEY was specified for the index and an INSERT statement that creates a duplicate key is executed, SQL Server issues a warning and ignores the duplicate row."
>>
>
>Thanks. What does CREATE UNIQUE (constraint) in the same Enterprise Tools dialog do?