Unique Index vs. Unique Constraint

• meichner

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  December 12, 2007 at 8:32 am

  #177500

  I have been having trouble locating the answer to a question. When I add a Unique Constraint to a field on a table, does that automatically create a Non Clustered Index on that field?

  Thanks

• TimothyAWiseman

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  December 12, 2007 at 8:38 am

  #759432

  meichner (12/12/2007)

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  I have been having trouble locating the answer to a question. When I add a Unique Constraint to a field on a table, does that automatically create a Non Clustered Index on that field?

  Thanks

  Yes, at least in SQL Server 2000 and 2005. I cannot speak for earlier versions or other flavors of SQL, but in those two at least a unique constraint is enforced by creating a unique index. There is a reference at http://msdn2.microsoft.com/en-us/library/ms177420.aspx

  Edited to add the url tag I forgot the first time.

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  Timothy A Wiseman
  SQL Blog: http://timothyawiseman.wordpress.com/

• meichner

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  December 12, 2007 at 8:49 am

  #759439

  Thanks for the fast response.