Robert,
> delete * from foo where not (foo.a = bar.a and foo.b=bar.b and
> foo.c=bar.c) ;
>
> so i end up with
>
> postgres=# select * from foo;
> a | b | c | d
> ---+---+---+---
> 1 | 2 | 4 | A
> 4 | 5 | 6 | b
> (2 rows)
>
> but thats not valid sql, is there some way to accomplish this?
Um, your example result doesn't match your pseudo-query. Assuming that you
want to delete everything that DOES match, not everything that DOESN'T, do:
DELETE FROM foo
WHERE EXISTS ( SELECT bar.a FROM bar
WHERE bar.a = foo.a AND bar.b = foo.b
AND bar.c = foo.c );
--
-Josh Berkus
Aglio Database Solutions
San Francisco