oracle 遍历每字符串的每一个字符

declare
v_str varchar2(50):='00xxx';
v_char varchar2(50):=null;
v_count number(10):=0;
begin
  v_count:=length(v_str);
  for i in 1..v_count loop
    v_char:= substr(v_str,i,1);
    dbms_output.put_line(v_char);
  end loop;
end;