Oracle 去掉重復字符串

create or replace function remove_same_string(oldStr varchar2, sign varchar2) return varchar2 is

  /****************************************************
  ** Oracle去掉重復字符串
  ** 函數名稱：RemoveSameStr
  ** 參    數：【名稱】         【類型 】      【說明】
  **           oldStr           varchar2       要處理的字符串
  **           sign             varchar2       字符串分隔符
  ** 返 回 值：Result           varchar2       不包含重復子串的記錄
  ****************************************************/
  str          varchar2(2000);
  currentIndex number;
  startIndex   number;
  endIndex     number;

  type str_type is table of varchar2(30) index by binary_integer;
  arr    str_type;
  Result varchar2(1000);
begin
  -- 空字符串
  if oldStr is null then
    return('');
  end if;

  --字符串太長
  if length(oldStr) > 2000 then
    return(oldStr);
  end if;
  str := oldStr;

  currentIndex := 0;
  startIndex   := 0;

  loop
    currentIndex := currentIndex + 1;
    endIndex     := instr(str, sign, 1, currentIndex);
    if (endIndex <= 0) then
      exit;
    end if;
  
    arr(currentIndex) := trim(substr(str, startIndex + 1, endIndex - startIndex - 1));
    startIndex := endIndex;
  end loop;

  --取最后一個字符串:
  arr(currentIndex) := substr(str, startIndex + 1, length(str));

  --去掉重復出現的字符串:
  for i in 1 .. currentIndex - 1 loop
    for j in i + 1 .. currentIndex loop
      if arr(i) = arr(j) then
        arr(j) := '';
      end if;
    end loop;
  end loop;

  str := '';
  for i in 1 .. currentIndex loop
    if arr(i) is not null then
      str := str || sign || arr(i);
      --數組置空:
      arr(i) := '';
    end if;
  end loop;

  --去掉前面的標識符:
  Result := substr(str, 2, length(str));

  return(Result);
end remove_same_string;