[codeprada]

http://weblogs.sqlte...imary_keys.aspx

Quote

...he kept confusing primary keys with identity columns. They are not the same! An identity column may be a type of primary key, but a primary key is not an identity column; it is a set of columns that you define that determine what makes the data in your table unique. It defines your data. It may be an identity column, it may be a varchar column or a datetime column or an integer column, or it may be a combination of multiple columns.