Die onClick-Methode ist unnötig
Delphi-Quellcode:
procedure TForm1.AbfrageClick(Sender: TObject);
begin
IBDataSet1.SelectSQL.Text :='Select * from Tabelle;';
iBDataSet1.ModifySQL.Text := 'UPDATE Tabelle SET FELD = :FELD WHERE ID = :old_ID;';
IBDataSet1.Open;
end;