adoquery saber si es null

//************************************************************************
procedure TForm1.Button1Click(Sender: TObject);
var
SQLQuery, aux: string;
begin

  ADOQuery1.Active := false;
  ADOQuery1.SQL.Clear;

  SQLQuery:='select * from borrar limit 1';
  ADOQuery1.SQL.Add(SQLQuery);

  ADOQuery1.Active := true;

  if  ADOQuery1.RecordCount > 0 then
  begin

    if ADOQuery1.FieldByName('nombre').IsNull then
    begin
      ShowMessage('nombre es null');
    end
    else
    begin
      aux:=ADOQuery1.FieldByName('nombre').AsString;
      ShowMessage(aux);
    end;

  end;

  ADOQuery1.Active := false;

end;



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