I wasn't quite sure what you wanted, but here's something that you might find useful.
Schema with few entries:
CREATE TABLE ALOHA (
REALM_KEY VARCHAR(32) NOT NULL,
ROLE_KEY VARCHAR(32) NOT NULL,
FUNCTION_KEY VARCHAR(32) NOT NULL
);
INSERT INTO ALOHA VALUES ('1', '1', '1');
INSERT INTO ALOHA VALUES ('1', '1', '2');
INSERT INTO ALOHA VALUES ('1', '2', '1');
INSERT INTO ALOHA VALUES ('1', '2', '2');
INSERT INTO ALOHA VALUES ('1', '2', '3');
INSERT INTO ALOHA VALUES ('1', '2', '4');
Try to insert 3 entries (only one gets inserted):
INSERT INTO ALOHA (REALM_KEY, ROLE_KEY, FUNCTION_KEY)
SELECT * FROM (
SELECT '1' AS REALM_KEY, '2' AS ROLE_KEY, '1' AS FUNCTION_KEY
UNION ALL
SELECT '1', '2', '3'
UNION ALL
SELECT '1', '2', '5'
) s
WHERE NOT EXISTS
(SELECT 1 FROM ALOHA a
WHERE a.ROLE_KEY = s.ROLE_KEY
AND a.REALM_KEY = s.REALM_KEY
AND a.FUNCTION_KEY = s.FUNCTION_KEY);