with Query1 do begin
  if isoldn then edit
  else append;
  fieldbyname('Num').asinteger:=strtoint(trim(editNum.text));
  fieldbyname('GuestNum').asstring:=trim(frm2.EditNum.text);
  DataMod.Database1.StartTransaction;
  try
    applyupdates;//该步出错提示不能给数据库中'Num'赋为‘nil'(Num设为不空)
    Database1.Commit;
  except
    Database1.Rollback;
  end;
  commitupdates;
  isoldn:=true;
end;
窗体中有DBMemo1控件,通过datasource1,query1连接数据库中的text字段