Hi, Ours is a web-based application. We're trying to implement ON DUPLICATE IGNORE for one of our application table, named EMAILLIST. After a quick Google search, I'm finding the following "easy & convenient" single SQL statement syntax to follow with: INSERT INTO EMAILLIST (EMAIL) SELECT 'john@xxxxxxxxxxx' WHERE NOT EXISTS (SELECT 1 FROM EMAILLIST WHERE EMAIL = 'john@xxxxxxxxxxx'); My question is, in a single threaded INSERT, this will *definitely* work. Since ours is a web-based application, will this work out in a concurrent multi-threaded environment too? In other words, will it be truly unique when INSERT calls are concurrent? Regards, Gnanam -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general