Oracle 自定义聚合函数

create or replace type str_concat_type as object (
    cat_string varchar2(4000),
    static function ODCIAggregateInitialize(cs_ctx In Out str_concat_type) return number,
    member function ODCIAggregateIterate(self In Out str_concat_type,value in varchar2) return number,
    member function ODCIAggregateMerge(self In Out str_concat_type,ctx2 In Out str_concat_type) return number,
    member function ODCIAggregateTerminate(self In Out str_concat_type,returnValue Out varchar2,flags in number) return number
)
/

create or replace type body str_concat_type is
  static function ODCIAggregateInitialize(cs_ctx IN OUT str_concat_type) return number
  is
  begin
      cs_ctx := str_concat_type( null );
      return ODCIConst.Success;
  end;

  member function ODCIAggregateIterate(self IN OUT str_concat_type,
                                       value IN varchar2 )
  return number
  is
  begin
      --1. concat string
      self.cat_string := self.cat_string || ‘,‘|| value;
      -- 2.get union set
      -- if  instr(self.cat_string, value ) = 0 or self.cat_string is null then
      --        self.cat_string := self.cat_string || ‘,‘ || value ;
      -- else
      --        self.cat_string := self.cat_string ||‘‘ ;
      -- end if ;
      return ODCIConst.Success;
  end;

  member function ODCIAggregateTerminate(self IN Out str_concat_type,
                                         returnValue OUT varchar2,
                                         flags IN number)
  return number
  is
  begin
      returnValue := ltrim(rtrim(self.cat_string,‘,‘),‘,‘);
      return ODCIConst.Success;
  end;

  member function ODCIAggregateMerge(self IN OUT str_concat_type,
                                     ctx2 IN Out str_concat_type)
  return number
  is
  begin
      self.cat_string := self.cat_string || ‘,‘ || ctx2.cat_string;
      return ODCIConst.Success;
  end;

end;
/

CREATE OR REPLACE FUNCTION str_concat(input varchar2) RETURN varchar2
  PARALLEL_ENABLE
  AGGREGATE USING str_concat_type;
/

实现的功能和wm_concat一样。

原文地址：https://www.cnblogs.com/ayumie/p/10002486.html