On Mon, Oct 27, 2014 at 4:19 AM, Simon Slavin <[email protected]> wrote:
> A foreign key which points to the same table had not occurred to me, outside
> of abstract mathematical exercises. I think you've come up with an
> acceptable example of why I felt reluctant to condemn the practise.
If you can do a self-join, it stands to reason that you can use a
foreign key from one table to itself.
A trivial example would be a filesystem with directories implemented
as a single table of {parent inode, name, child inode, ...}.
Many of the traditional hierarchical examples used to show nested sets
and recursive queries should also qualify for having foreign keys from
one table to itself.
Nico
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