@classmethod
def make_views(cls, conn):
    """Create day_trips and day_stop_times views.

        day_trips:  day_trips2 x trips  = days x trips
        day_stop_times: day_trips2 x trips x stop_times = days x trips x stop_times
        """
    conn.execute('DROP VIEW IF EXISTS main.day_trips')
    conn.execute(
        'CREATE VIEW day_trips AS   SELECT day_trips2.*, trips.* FROM day_trips2 JOIN trips USING (trip_I);'
        )
    conn.commit()
    conn.execute('DROP VIEW IF EXISTS main.day_stop_times')
    conn.execute(
        'CREATE VIEW day_stop_times AS   SELECT day_trips2.*, trips.*, stop_times.*, day_trips2.day_start_ut+stop_times.arr_time_ds AS arr_time_ut, day_trips2.day_start_ut+stop_times.dep_time_ds AS dep_time_ut   FROM day_trips2 JOIN trips USING (trip_I) JOIN stop_times USING (trip_I)'
        )
    conn.commit()
