Hi- Let's say I have a base table B (with a PK id, say) and two derived tables D1 & D2 (with different cols). For a given B.id, I'd like to allow only a corresponding row in *either* D1 or D2, but not both. Any suggestions on how to do this? Should I not be using inheritance at all? My thought was to add a column inherits_to to B with a value indicating whether that row is really a D1 or a D2 and enforce it with appropriate CHECK constraints on each of the derived tables. Sorry if this is unclear... -- Peter Fein pfein@xxxxxxxxx 773-575-0694 Basically, if you're not a utopianist, you're a schmuck. -J. Feldman ---------------------------(end of broadcast)--------------------------- TIP 6: Have you searched our list archives? http://archives.postgresql.org