oarcle 提取数字函数

create or replace function get_number(str varchar2)
return varchar2 is
       v_rs varchar2(4000);
begin
  if str is null then
     return null;
  else
    for i IN 1 .. length(str) loop
    if ascii(substr(str, i, 1)) between 48 and 57 then
    v_rs := v_rs || substr(str, i, 1);
  end if;
      end loop;
  return v_rs;
  end if;
end;
select get_number('aa2') from dual;