Steve Jones - SSC Editor (2/20/2015)
I user request to get an article, which would explain in details the differences between primary key and unique index, especially from disk i/o point of view, I think it will be of a massive help to many SQL Server Central readers.
Are you sure you're not getting PKs and Unique indexes mixed up with Clustered and Non-Clustered Indexes here?
--Jeff Moden
Change is inevitable... Change for the better is not.