oracle如何去除字符串中的重复字符

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

   /****************************************************
   ** Oracle去掉重复字符串
   ** 函数名称：RemoveSameStr
   ** 参    数：【名称】         【类型 】      【说明】
   **           oldStr           varchar2       要处理的字符串
   **           sign             varchar2       字符串分隔符
   ** 返 回 值：Result           varchar2       不包含重复子串的记录
   ****************************************************/
   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;  

   --字符串太长
   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;  

   --取最后一个字符串:
   arr(currentIndex) := substr(str, startIndex + 1, length(str));  

   --去掉重复出现的字符串:
   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);
       --数组置空:
       arr(i) := '';
     end if;
   end loop;  

   --去掉前面的标识符:
   Result := substr(str, 2, length(str));  

   return(Result);
 end remove_rame_string;

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

  /****************************************************
  ** Oracle去掉重复字符串
  ** 函数名称：RemoveSameStr
  ** 参    数：【名称】         【类型 】      【说明】
  **           oldStr           varchar2       要处理的字符串
  **           sign             varchar2       字符串分隔符
  **           newStr           varchar2       新添加的字符串，以逗号隔开
  ** 返 回 值：Result           varchar2       不包含重复子串的记录
  ****************************************************/
  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('[' || newStr || ']');
  end if;

  --字符串太长
  if length(oldStr) > 2000 then
    return(oldStr);
  end if;
  str := oldStr;
  --拼接字符串,在"]"之前添加新创建的字符串
  str := substr(str, 0, instr(str, ']')-1) || ','||newStr;
  str := substr(str, instr(str, '[')+1, length(str));

  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;

  --取最后一个字符串:
  arr(currentIndex) := substr(str, startIndex + 1, length(str));

  --去掉重复出现的字符串:
  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);
      --数组置空:
      arr(i) := '';
    end if;
  end loop;

  --去掉前面的标识符:
  Result := substr(str, 2, length(str));

  return('[' || Result || ']');
end remove_rame_string;

UPDATE TEST_CLOB set "STR" = remove_rame_string(STR, ',', '"str1","str2", "str2", "str3"') WHERE ID='';

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