drop table t purge

create table t as select '123,456,789' acct from dual

select distinct (instr(acct||',',',',1,level)) loc
from t
connect by level <= length(acct)- length(replace(acct,','))+1

select substr(acct,
              nvl(lag(loc) over ( order by loc),0)+1,
              loc-nvl(lag(loc) over ( order by loc),0)-1
             ) list_as_rows
from (
   select distinct (instr(acct||',',',',1,level)) loc
   from t
   connect by level <= length(acct)-length(replace(acct,','))+1
), t