In our dbms class, these were the four properties of a primary key discussed for Oracle. Unique Not NULL Fully functional dependency Indexed I understand all the properties except the 3rd one ...
From various posts, I have summarized about using number type instead of char/varchar for PK: If you choose char/varchar type for PK and your values are short (just some alpha numberic codes) then it ...
In MS SQL Server, it is well documented that the type of the primary key can have a dramatic effect on performance. Using narrower types and sequential values significantly improves insert performance ...