Say I have a table, say my_table, that is self-referencing. It looks like this : id integer pk, orig_id integer references my_table(id), . . . Now this set of rows would be legal id/orig_id 1 /1 2/1 3/1 4/4 5/4 but this not: id/orig_id 1 /1 2/1 3/1 4/1 5/4 in other words: the row pointed to by orig_id cannot reference any row other than itself. How might I implement this as a constraint? thanks, Daniel
