Danny,

Thanks for the thoughtful and well-documented post. Your English is fine and please be assured that most people visiting this site are aware that it has an international following and that English is not the primary language for many of those posting here.

One thing about using a primary key constraint that makes it less attractive is that it does still lock the row for that key. Although in the original article, a variety of keys are supported in the table, the main difficulty arises when multiple users are running the same code. They would still experience blocking on their chosen key row. A user obtaining a value for key "PR1" in your code would not have a conflict with one obtaining a value for "PR2", but would still block a second user also looking for a "PR1" value.