câu hỏi cơ sở dữ liệu trong sql

String query = "SELECT r.reservation_no, f.flight_no, r.departure_date, f.departure_time, f.duration FROM flights f, reservations r WHERE f.flight_no=r.flight_no AND r.customer_ssn="?" ";

PreparedStatement ps = connection.prepareStatement(query);
ps.setString(1, customer_ssn);
result = ps.executeQuery();