On Thu, 21 Jun 2001 zilch(at)home(dot)se wrote:
>
> Is it possible to have a foreign key to a non-primary key (also
> meaning non-unique and therefore non-indexed) column i a table?
Generally no. It's not allowed by the spec, so as of 7.1, we
prevent it. Admittedly, you could pull the rug out from underneath
it by dropping the index, though.