def check_if_scenario_name_exists(conn, scenario_name):
    """
    :param conn: the database connection
    :param scenario_name: str; the scenario name
    :return: scenario_id; str or None
    """
    c = conn.cursor()

    sql = "SELECT scenario_id FROM scenarios WHERE scenario_name = ?"
    query = c.execute(sql, (scenario_name,)).fetchone()

    if query is None:
        scenario_id = None
    else:
        scenario_id = query[0]

    c.close()

    return scenario_id