Ok, I am sorry for the 99.99 % thing, I misunderstood what u meant by that.
But an information that can be useful for you for later is that composite
primary key can be very useful for expressing a many to many relationships
between 2 tables.
Let's take a football (soccer if u are on the other side of the ocean)
example.
One league can have more than one team. But one team can belong to more than
one league. For example, the English Premier League (EPL) got obviously more
than one team. But one team can belong to more than one league as it could
belong for example to the EPL and the UEFA Champion's League.
But still you cannot permit that the same team / league combination appears
2 times in the DB as it would mean that one team appears 2 times in the same
league which obviously does not make sense. You then need to have a
composite Primary key to make that impossible to happen.
I hope that helps you understanding Composite PK. There are a lot of
litterature about it all over the internet if you want to see example and
all, it really worth it as you often need it in real world applications.
Cheers
Francois.
PS: By the way what does "noob" mean?
"-Karl" <di*****@gmail.com> wrote in message
news:11**********************@f14g2000cwb.googlegr oups.com...
I'll have to see what you mean as I always understood DB's to be able
to have only 1 primary key to make sure there is absolutly no chance of
duplicates / data corruption.
what I meant by the 99.99% is that I was 99.99% sure that all db's
would have only 1 primary key.
I haven't touched upon composite PK so I do not know anything about
that terminology. Thanks for pointing it out. I'm just a noob :)