Setting primary key on existing table - Mailing list pgsql-novice

I would like to be able to redefine a field in a table to be a foreign
reference -- however this field was initially defined as just "serial" and
not "serial primary key".  I tried to add that constraint to the table, but
it didn't work.  Do I need to copy out the table, drop it, and recreate it
with this constraint in order for it to be a foreign key?

Thanks
--
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Doug Silver
Network Manager
Urchin Software Corp.    http://www.urchin.com
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~