SELECT P.pub_name FROM pubs..publishers P
WHERE ISNULL(P.state, '__') IN
(
SELECT ISNULL(state, '__') FROM pubs..publishers
EXCEPT
SELECT ISNULL(state, '__') FROM pubs..authors
)

SELECT P.pub_name FROM pubs..publishers P
WHERE NOT EXISTS
(SELECT * from pubs..authors A 
WHERE A.state = P.state
OR (A.state IS NULL AND P.state IS NULL))
a
b
