oracle function ( number increment )

CREATE OR REPLACE FUNCTION TS.F_Seq RETURN VARCHAR2 IS
tmpSEQ NUMBER;
rtnSEQ VARCHAR2(12);

BEGIN
   tmpSEQ := 0;
   rtnSEQ := '';

    SELECT NVL(TO_NUMBER(SUBSTR(MAX(SEQNO),12)),0) INTO tmpSEQ FROM TB__MASTER
    WHERE SEQNO LIKE TO_CHAR(SYSDATE,'YYYYMMDD') || '%';

    SELECT TO_CHAR(SYSDATE, 'YYYYMMDD') || '-' || LPAD(TO_CHAR(tmpSEQ+1),3,'0') INTO rtnSEQ FROM DUAL;

   RETURN rtnSEQ;

   EXCEPTION
     WHEN NO_DATA_FOUND THEN
          RETURN TO_CHAR(SYSDATE, 'YYYYMMDD') || '-001';

     WHEN OTHERS THEN
       -- Consider logging the error and then re-raise
       RAISE;
END F_Seq;
/