> Почему-то во многих СУБД ЭТО :-) присутствует. Видимо, не
> зря...


ну вот касательно оракла:

"Primary keys are supposed to be imutable, never changing, constant.  It is an excessively
bad practice to have to update them ever.  If there is a 0.00001% chance you will have to
update a primary key -- then it is not a primary key, its a surrogate key and you need to
find the true primary key (even if you have to make it up via a sequence) "

http://asktom.oracle.com/pls/asktom/f?p=100:11:0::::P11_QUESTION_ID:5773459616034

> Игорь Шевченко  (13.06.2011 20:54:20)  [20]

Оракл всегда стоял особняком.