RUNNING NO STRING ใครเซียน database qry บ้างครับ รองเข้ามาดูหน่อย

CREATE TABLE TBL_X(NO NVARCHAR2(15));

INSERT INTO TBL_X (NO) VALUES ('กขค.2557/000002');
INSERT INTO TBL_X (NO) VALUES ('กขค.2557/000003');
INSERT INTO TBL_X (NO) VALUES ('กขค.2557/000004');
INSERT INTO TBL_X (NO) VALUES ('กขค.2557/000005');
INSERT INTO TBL_X (NO) VALUES ('กขค.2557/000006');
INSERT INTO TBL_X (NO) VALUES ('กขค.2557/000007');
INSERT INTO TBL_X (NO) VALUES ('กขค.2557/000008');
INSERT INTO TBL_X (NO) VALUES ('กขค.2557/000009');
INSERT INTO TBL_X (NO) VALUES ('กขค.2557/000010');
INSERT INTO TBL_X (NO) VALUES ('กขค.2557/000012');
INSERT INTO TBL_X (NO) VALUES ('กขค.2557/000013');
INSERT INTO TBL_X (NO) VALUES ('กขค.2557/000015');

SELECT * FROM (SELECT ct.NO FROM TBL_X_TMP ct  WHERE ct.NO<(SELECT MAX(CAST(REGEXP_SUBSTR(NO,'[^/]+',2,2) AS INTEGER)+2) FROM TBL_X)
MINUS
SELECT c2.NO FROM (SELECT CAST(REGEXP_SUBSTR(NO,'[^/]+',2,2) AS INTEGER) AS NO FROM TBL_X c
) c2
) WHERE ROWNUM=1