Merlin Moncure <mmoncure@gmail.com> writes:
> On Sat, Jun 6, 2009 at 2:07 PM, Tom Lane<tgl@sss.pgh.pa.us> wrote:
>> If you're willing to use a trigger, just insert the one allowed row
>> and then install a trigger that throws error for any insert or delete
>> attempt ...
> what if you need to delete then insert? :-)
Hmm ... I supposed the requirement was "always exactly one row".
If it's "always zero or one row", then you're right.
regards, tom lane