扩展oracle，sum函数，遇见字符换max

  select e.user_id,decode(to_char(e.datatype),'3',max(e.cell_value),'2',f_sum(e.cell_value)) cell_value
  from e_1099310300000000002 e 
  group by e.user_id,atd.datatype

这样的话就不用管sum(e.cell_value)是字符就不会报ora-01722错了，当然也可以合并，这里需求是取max不是合并

create or replace type t_sum as object (
--author lidongbo
  var varchar2(999),
  static function ODCIAggregateInitialize(sctx In Out t_sum) return number,
  member function ODCIAggregateIterate(self In Out t_sum, value In varchar2) return number,
  member function ODCIAggregateMerge(self In Out t_sum, ctx2 In t_sum) return number,
  member function ODCIAggregateTerminate(self In Out t_sum, returnValue Out varchar2, flags In varchar2) return number
) 

create or replace type body t_sum is
--author lidongbo
static function ODCIAggregateInitialize (sctx In Out t_sum)
return number is
       begin
            sctx := t_sum(0);
            return ODCIConst.Success;
       end;   
   
member function ODCIAggregateIterate (self In Out t_sum, value In varchar2)
return number is
       begin
            self.var := self.var + value;
            return ODCIConst.Success;
            EXCEPTION
            WHEN OTHERS THEN
            IF SELF.var < VALUE THEN
                SELF.var := VALUE;
            END IF;
            return ODCIConst.Success;
       end;
       
member function ODCIAggregateMerge(self In Out t_sum, ctx2 In t_sum)
return number is
       BEGIN
           self.var := self.var;
            return ODCIconst.Success;
       end;
       
member function ODCIAggregateTerminate(self In Out t_sum, returnValue Out varchar2, flags In varchar2)
return number is
       begin
            returnValue := self.var;
            return ODCIConst.Success;
       end;

end;

CREATE OR REPLACE FUNCTION f_sum(input varchar2 )
--author lidongbo
RETURN varchar2
PARALLEL_ENABLE AGGREGATE USING t_sum;