Uses System.JSON;

Var    

FDQuery : TFDQuery;

field_name,Collumnname,CollumnValue : String;

I: Integer;

LJSONObject:TJsonObject;

begin

    FDQuery := TFDQuery.Create(nil);

    try

      FDQuery.Connection := FDConnection1;

      FDQuery.SQL.Text := query;

      FDQuery.Active := True;

      FdQuery.BeginBatch;//Don't update external references until EndBatch;

      FDQuery.First;

      LJSONObject:= TJSONObject.Create;

      while (not FDQuery.EOF) do

      begin

            for I := 0 to FDQuery.FieldDefs.Count-1 do

            begin

              CollumnName  := FDQuery.FieldDefs[I].Name;

              CollumnValue := FDQuery.FieldByName(CollumnName).AsString;

              LJSONObject.AddPair(TJSONPair.Create(TJSONString.Create( CollumnName),TJSONString.Create(CollumnValue)));

          end;

  FDQuery.Next;

          //FDQuery.Refresh; that's wrong

         FdQuery.EndBatch;

        finally 

          FDQuery.Free;

          Showmessage(LJSonObject.ToString);

        end;

    end;