2010/5/4 Grzegorz Jaśkiewicz <gryzman@gmail.com>:
>
> Another thing, If your PK changes, it is no longer a PK, you can't rely on it.
Depending upon what you mean by changes this could be true or it could
be a matter of opinion. If your referring to a candidate key's value
changes, this key still provides a useful way to identify a tuple.
Also, just because a surrogate key is a useful way to identify a row,
by itself it does nothing to uniquely identify an entity that a row
represents. On some DBMS forums that I frequent, it is a daily
occurrence to see questions on how to eliminate duplicate rows. So,
for some people, there are times when even surrogate keys cannot be
relied upon as a PK.
--
Regards,
Richard Broersma Jr.
Visit the Los Angeles PostgreSQL Users Group (LAPUG)
http://pugs.postgresql.org/lapug
