In response to Robert Edwards : > Can anyone suggest a way that I can impose uniqueness on a and b when > c is NULL?
Sure, use a functional index: test=# create table bobtest (a int, b int, c int); CREATE TABLE test=*# create unique index idx_bobtest on bobtest(a,b,coalesce(c::text,'NULL')); CREATE INDEX test=*# insert into bobtest (a, b) values (1, 4); INSERT 0 1 test=*# insert into bobtest (a, b, c) values (1, 4, NULL); ERROR: duplicate key value violates unique constraint "idx_bobtest" test=!# Regards, Andreas -- Andreas Kretschmer Kontakt: Heynitz: 035242/47150, D1: 0160/7141639 (mehr: -> Header) GnuPG-ID: 0x3FFF606C, privat 0x7F4584DA http://wwwkeys.de.pgp.net -- Sent via pgsql-sql mailing list (pgsql-sql@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-sql
