Rows to columns conversion:

(SELECT LIST.tm

   FROM (WITH rec AS

              (SELECT '1,2,3,4,5' tm

                 FROM DUAL)

         SELECT     REGEXP_SUBSTR (tm, '[^,]+', 1, LEVEL) tm

               FROM rec

         CONNECT BY LEVEL <= (SELECT LENGTH (REPLACE (tm, ',', NULL))

                                FROM rec)) LIST

  WHERE LIST.tm IS NOT NULL) 

Union and union all:

(SELECT LIST.tm

   FROM (WITH rec AS

              (SELECT '1,2,3,4,5' tm

                 FROM DUAL)

         SELECT     REGEXP_SUBSTR (tm, '[^,]+', 1, LEVEL) tm

               FROM rec

         CONNECT BY LEVEL <= (SELECT LENGTH (REPLACE (tm, ',', NULL))

                                FROM rec)) LIST

  WHERE LIST.tm IS NOT NULL)   

  union all     

 (SELECT LIST.tm

   FROM (WITH rec AS

              (SELECT '1,2,3,4,5,6' tm

                 FROM DUAL)

         SELECT     REGEXP_SUBSTR (tm, '[^,]+', 1, LEVEL) tm

               FROM rec

         CONNECT BY LEVEL <= (SELECT LENGTH (REPLACE (tm, ',', NULL))

                                FROM rec)) LIST

  WHERE LIST.tm IS NOT NULL)