Is something like this what you are trying to do?
somedb=# create table a (a int, b text, c date);
CREATE TABLE
somedb=# create table b (a int, b text, c date);
CREATE TABLE
somedb=# select * from a join b using (a, b, c);
a | b | c
---+---+---
(0 rows)
somedb=# insert into a values (1, 'test', now());
INSERT 0 1
somedb=# insert into b values (1, 'test', now());
INSERT 0 1
somedb=# insert into b values (2, 'test', now());
INSERT 0 1
somedb=# select * from a join b using (a, b, c);
a | b | c
---+------+------------
1 | test | 2011-09-28
(1 row)
Best wishes,
Chris Travers
