Should be easy enough to get this result (or is it possible?)...

I think the following code explains my problem more elegantly than I
could ever hope to try and explain in a reasonable amount of words.
The upshot of things being that I want the 2nd query below (f.foo =
'b') to return foo_id and foo. Am I missing something? My head
stands poised to get clobbered with the clue-bat. Here's the test
case:

CREATE TABLE foo ( foo_id SERIAL NOT NULL, foo VARCHAR(32) NOT NULL );
CREATE TABLE bar ( bar_id SERIAL NOT NULL, foo_id INT NOT NULL, bar VARCHAR(32) NOT NULL);
INSERT INTO foo (foo) VALUES ('a');
INSERT INTO foo (foo) VALUES ('b');
INSERT INTO foo (foo) VALUES ('c');
INSERT INTO bar (foo_id, bar) VALUES ('1','x');
INSERT INTO bar (foo_id, bar) VALUES ('1','y');
INSERT INTO bar (foo_id, bar) VALUES ('1','z');
INSERT INTO bar (foo_id, bar) VALUES ('2','x');
INSERT INTO bar (foo_id, bar) VALUES ('2','z');

SELECT f.foo_id, f.foo, b.bar_id, b.bar
FROM foo AS f LEFT JOIN bar AS b on (f.foo_id = b.foo_id)
WHERE (b.bar ISNULL OR b.bar = 'y') AND f.foo = 'a';
foo_id | foo | bar_id | bar
--------+-----+--------+-----
1 | a | 2 | y
(1 row)

SELECT f.foo_id, f.foo, b.bar_id, b.bar
FROM foo AS f LEFT JOIN bar AS b on (f.foo_id = b.foo_id)
WHERE (b.bar ISNULL OR b.bar = 'y') AND f.foo = 'b';
foo_id | foo | bar_id | bar
--------+-----+--------+-----
(0 rows)

SELECT f.foo_id, f.foo, b.bar_id, b.bar
FROM foo AS f LEFT JOIN bar AS b on (f.foo_id = b.foo_id)
WHERE (b.bar ISNULL OR b.bar = 'y') AND f.foo = 'c';
foo_id | foo | bar_id | bar
--------+-----+--------+-----
3 | c | |
(1 row)

Any help/ideas/suggestions? -sc

--
Sean Chittenden