> Can someone explain to me what is the advantage of a one-to-one
> relationship ? I don't see any advantage on it, because a single record

in

> the first table is related to only one record in the second table, so why
> don't put it all in one table then ?

I'll put you an example for which I'm doing a one-to-one relationship, I
have a database with medical patients information, for security and privacy
reasons, I have personal data of the pacient in one table and the medical
data in other. With these, you can have different access privilegies for
different users that can manage only certain type of data. Yes, you can do
the same with a view, but I think having the data in more than one table
simplifies the problem (and also, politicians want us to do it that way ;)

Maybe you can imagine some other uses for having different type of data in
different tables (tables are easier to manage, with few columns they have
faster access, etc.)

Jordi