Re: Question: unique on multiple columns

On Thu, Feb 06, 2003 at 10:33:51 -0600,
  will trillich <will@serensoft.com> wrote:
>
> of course, my example is rather bogus -- as others pointed out,
> unique(a,c) means that there'll only be 1 b for any a/c pair, so
> the unique(b...) index is not-too-useful. it's just an
> illustration, and a bad one at that. ah, well...

If there are several different foreign key references into the table
using different combinations of a, b and c, you might need both indexes.