Unique key vs. unique index on SQL Server 2008

Question

I have a table called countries and I define the country_name column to be unique by creating a “Index/Key” of type “Unique Key” on SQL Server 2008 R2.

Answer 1

There is no difference between unique index or a unique constraint and also there is no performance difference. However there are some differences for creation where some index creation options are not available for unique constraints.