>The primary key should NOT be entered by the user... the program should create this key. If you have another unique value that the user keys (SSN, phone, etc) , this could be a candidate key. The primary key does not have to be shown to the user at all... it should be an integer that simply relates the records in the table. If you control the assignment of the keys, there is no way that two separate users can collide.

Aren't you now required to mention Walter's view at this point?