My query in oracle is
INSERT INTO TRAVEL(LOGIN_ID, LOCK_SESSION_ID, LOCK_OPERATION, LOCK_KEY1 ,USER_NAME ) SELECT 'RAM','CD7F','TER','21','null' from DUAL where not exists ( SELECT * FROM TRAVEL A WHERE A.LOCK_OPERATION = 'TER' AND LOCK_KEY1 = '21');
can u help me to ececute same query in postgresql
