CREATE TABLE REFAB ( REFFAB_STR VARCHAR2(60))

INSERT INTO REFAB(REFFAB_STR) VALUES ('1510029-1001');

INSERT INTO REFAB(REFFAB_STR) VALUES ('1410029M-1001');

INSERT INTO REFAB(REFFAB_STR) VALUES ('008-R230-B206');



SELECT REPLACE(REFFAB_STR,'-','-RF-') FROM REFAB;

-- I am getting the result as below

REPLACE(REFFAB_STR,'-','-RF-')
1510029-RF-1001
1410029M-RF-1001
008-RF-R230-RF-B206

--i want the result to be like below.

1510029-RF-1001
1410029M-RF-1001
008-RF-R230-B206