SELECT t1.*,
       TRIM (SUBSTR (',' || t1.tcd,INSTR (',' || t1.tcd, ',', 1, rn) + 1,
INSTR (',' || t1.tcd, ',', 1, rn + 1)- 1- INSTR (',' || t1.tcd, ',', 1, rn))) tcd_single
  FROM (SELECT md.*, LENGTH (tcd) - LENGTH (REPLACE (tcd, ',', '')) lll
          FROM (SELECT '123,456,789,' tcd
                  FROM DUAL) md) t1,
       (SELECT ROWNUM rn
          FROM all_objects
         WHERE ROWNUM < 1000) t2
 WHERE t2.rn <= t1.lll

  SELECT distinct REGEXP_SUBSTR('123,234,456', '[^' || ',' || ']+', 1, LEVEL) a
   FROM dual
   CONNECT BY REGEXP_SUBSTR('123,234,456', '[^' || ','  || ']+', 1, LEVEL) IS NOT NULL
   ORDER BY a

  SELECT distinct REGEXP_SUBSTR('123,234,456', '\d+', 1, LEVEL) a, LEVEL
   FROM dual
   CONNECT BY REGEXP_SUBSTR('123,234,456', '\d+', 1, LEVEL) IS NOT NULL
   ORDER BY a