大家来帮我看看下面查询模块的代码，查询之前DBGridEh1中显示的是当前表中所有记录，执行查询后DBGridEh1中显示的记录不变，通过测试发现查询语句能正确执行，但用了很多方法都不能刷新数据到DBGridEh1中显示。（插入、修改、删除操作执行完后DBGridEh1都能正确显示更新后的记录）

procedure TF_Main.Button4Click(Sender: TObject);
var strata1,strata2: string;
    pc:pchar;
begin
  strata1:=trim(Combobox1.Text);
  strata2:=trim(Combobox2.Text);

  if strata2='' then
    begin
      if strata1='' then
        begin
          Messagebox(handle,'请选择机型或填入功能危险编号！','提示',MB_OK);
          exit;
        end
      else
        begin
          DataModule_Navig.ADODataSet_AircraftFailure.Close;
          DataModule_Navig.ADODataSet_AircraftFailure.CommandText:='select * from TAB_FHA_AircraftFailure where TAB_FHA_AircraftFailure.Aircraft='''+strata1+'''';
          DataModule_Navig.ADODataSet_AircraftFailure.Open;
          pc := pchar(IntToStr(DataModule_Navig.ADODataSet_AircraftFailure.RecordCount));
          Messagebox(handle,pc,'提示',MB_OK);
          DBGridEh1.Refresh;
          if DataModule_Navig.ADODataSet_AircraftFailure.RecordCount=0 then
          messagebox(handle,'无此机型记录','提示',MB_OK);
        end
    end
  else
    begin
      if strata1='' then
        begin
          DataModule_Navig.ADODataSet_AircraftFailure.Close;
          DataModule_Navig.ADODataSet_AircraftFailure.CommandText:='select * from TAB_FHA_AircraftFailure where TAB_FHA_AircraftFailure.No='''+strata2+'''';
          DataModule_Navig.ADODataSet_AircraftFailure.Open;
          pc := pchar(IntToStr(DataModule_Navig.ADODataSet_AircraftFailure.RecordCount));
          Messagebox(handle,pc,'提示',MB_OK);
          if DataModule_Navig.ADODataSet_AircraftFailure.RecordCount=0 then
          messagebox(handle,'无此功能危险编号记录','提示',MB_OK);
        end
      else
        begin
          DataModule_Navig.ADODataSet_AircraftFailure.Close;
          DataModule_Navig.ADODataSet_AircraftFailure.CommandText:='select * from TAB_FHA_AircraftFailure where TAB_FHA_AircraftFailure.No='''+strata2+''' and TAB_FHA_AircraftFailure.Aircraft='''+strata1+'''';
          DataModule_Navig.ADODataSet_AircraftFailure.Open;
          pc := pchar(IntToStr(DataModule_Navig.ADODataSet_AircraftFailure.RecordCount));
          Messagebox(handle,pc,'提示',MB_OK);
          if DataModule_Navig.ADODataSet_AircraftFailure.RecordCount=0 then
          messagebox(handle,'此机型下无此功能危险编号记录','提示',MB_OK);
        end
    end
  

end;