ORA-00904: 无效列名(100分)

三层，中间用ado2.6,客户端用dbgrid连接clientdataset,直接在dbgrid中输入能正常提交，
但在clientdataset的beforpost中计算有关字段后用clientdataset.fieldvalues[]添加到
字段中却出现如下错误,用applyupdates提交
ORA-00904: 无效列名

因为你的ClientDataSet有连接数据库，
把你的ADOConnection.KeepConnection := False;
只计算并不提交

clientdataset3.Close;
clientdataset3.CommandText:='select COSTGAS from STATION1 where (UNITENO='''+fieldvalues['uniteno']+''')and(EDATE=to_date('''+date2+''',''yyyy-mm-dd''))';
clientdataset3.open;
clientdataset3.First;
SS:=0;
while not clientdataset3.Eofdo
begin
if clientdataset3.FieldValues['COSTGAS']<>null then
SS:=SS+clientdataset3.FieldValues['COSTGAS'];
clientdataset3.Next;
end;
clientdataset3.Close;
clientdataset1FieldValues['COSTGAS']:=ss;
然后post;
然后clientdataset1.applyupdates(0)提示无效列名的；

接受答案了.