Oracle自定义聚合函数实现字符串连接的聚合

create or replace type string_sum_obj as object (
--聚合函数的实质就是一个对象
     sum_string varchar2(4000),
     static function ODCIAggregateInitialize(v_self in out string_sum_obj) return number,
     --对象初始化
     member function ODCIAggregateIterate(self in out string_sum_obj, value in varchar2) return number,
     --聚合函数的迭代方法(这是最重要的方法)
     member function ODCIAggregateMerge(self in out string_sum_obj, v_next in string_sum_obj) return number,
     --当查询语句并行运行时,才会使用该方法,可将多个并行运行的查询结果聚合
     
     member function ODCIAggregateTerminate(self in string_sum_obj, return_value out varchar2 ,v_flags in number) return number
     --终止聚集函数的处理,返回聚集函数处理的结果.
)
/
create or replace type body string_sum_obj is
     static function ODCIAggregateInitialize(v_self in out string_sum_obj) return number is
     begin
         v_self := string_sum_obj(null);
         return ODCICONST.Success;
     end;
     member function ODCIAggregateIterate(self in out string_sum_obj, value in varchar2) return number is
     begin
          /* 连接 */   
          self.sum_string := self.sum_string || value;
          return ODCICONST.Success;
          /* 最大值 */
          if self.sum_string<value then
              self.sum_string:=value;
          end if;
          /* 最小值 */
          if self.sum_string>value then
       self.sum_string:=value;          
          end if;
          
          return ODCICONST.Success;
     end;
     member function ODCIAggregateMerge(self in out string_sum_obj, v_next in string_sum_obj) return number is
     begin
          /* 连接 */   
          self.sum_string := self.sum_string || v_next.sum_string;
          return ODCICONST.Success;
          /* 最大值 */
          if self.sum_string<v_next.sum_string then
              self.sum_string:=v_next.sum_string;
          end if;

          /* 最小值 */
          if self.sum_string>v_next.sum_string then
              self.sum_string:=v_next.sum_string;          
          end if;
          
          return ODCICONST.Success;
     end;
     member function ODCIAggregateTerminate(self in string_sum_obj, return_value out varchar2 ,v_flags in number) return number is
     begin
          return_value:= self.sum_string;
          return ODCICONST.Success;
     end;
end;
/
create or replace function ConnStrSum(value Varchar2) return Varchar2
     parallel_enable aggregate using string_sum_obj;