Hello Helen,

>The execution plans will be better because you avoid the duplicate
>indexes; but if you want to keep the RI in formal constraints, then use
>surrogate primary keys for the optional 1:1 relations and then *do* have
>the foreign keys. This also gives more flexibility if you have other
>dependencies.

Thanks Helen. I like this one :)

--
Best regards,
Alexander mailto:saho@...