how to use aggregate functions when combining two datatables

 DataSet3 dataSet2 = new DataSet3();

 DataTable baraniotselect = dataSet2.baraniotselect;
 DataTable PocKrajRazl1 = dataSet2.PocKrajRazl1;
 DataTable Table1 = dataSet2.Table1;

 string comstring3="SELECT PocKrajRazl1.DATA, PocKrajRazl1.GBRV, Max(IIf([baraniotselect].[DATA]=[PocKrajRazl1].[DATA],[baraniotselect].[Gorivo],0)) AS Gorivo1, Max(IIf([baraniotselect].[DATA]=[PocKrajRazl1].[DATA],[baraniotselect].[Addblue],0)) AS Addblue1, Max(IIf([baraniotselect].[DATA]=[PocKrajRazl1].[DATA],[baraniotselect].[Antifriz],0)) AS Antifriz1, Max(IIf([baraniotselect].[DATA]=[PocKrajRazl1].[DATA],[baraniotselect].[Motmaslo],0)) AS Motmaslo1, PocKrajRazl1.pockm, PocKrajRazl1.krajkm,  Max(PocKrajRazl1.Poslprov) AS MaxOfPoslprov, Max(PocKrajRazl1.Poslserv) AS MaxOfPoslserv, Max(PocKrajRazl1.KMS) AS MaxOfKMS, Max(PocKrajRazl1.KMP) AS MaxOfKMP FROM PocKrajRazl1 LEFT JOIN baraniotselect ON PocKrajRazl1.GBRV = baraniotselect.GBR WHERE (((baraniotselect.GBR)=[PocKrajRazl1].[GBRV])) GROUP BY PocKrajRazl1.DATA, PocKrajRazl1.pockm, PocKrajRazl1.krajkm ORDER BY PocKrajRazl1.DATA";

command.CommandText = comstring3;

OleDbDataAdapter oleDBDataAdapter1 = new OleDbDataAdapter();
dataSet2.Clear();
              
                    oleDBDataAdapter1.SelectCommand = command1;
                    oleDBDataAdapter1.Fill(dataSet2, "baraniotselect");
                    oleDBDataAdapter1.SelectCommand = command2;
                    oleDBDataAdapter1.Fill(dataSet2, "PocKrajRazl1");
                    oleDBDataAdapter1.SelectCommand = command;
                    oleDBDataAdapter1.Fill(dataSet2, "Table1");

but I received this error message OleDbException was unabled:

"An action query cannot be used as a row source."