CREATE TABLE flight_stop (flight_id NUMBER, stop_number NUMBER, stop_days CLOB, stop_airport CLOB, arrival_time NUMBER, arrival_airline CLOB, arrival_flight_number NUMBER, departure_time NUMBER, departure_airline CLOB, departure_flight_number NUMBER, stop_time NUMBER)
CREATE TABLE month (month_number NUMBER, month_name CLOB)
CREATE TABLE flight_fare (flight_id NUMBER, fare_id NUMBER)
CREATE TABLE fare_basis (fare_basis_code CLOB, booking_class CLOB, class_type CLOB, premium CLOB, economy CLOB, discounted CLOB, night CLOB, season CLOB, basis_days CLOB)
CREATE TABLE airline (airline_code VARCHAR2, airline_name CLOB, note CLOB)
CREATE TABLE airport (airport_code VARCHAR2, airport_name CLOB, airport_location CLOB, state_code VARCHAR2, country_name VARCHAR2, time_zone_code VARCHAR2, minimum_connect_time NUMBER)
CREATE TABLE equipment_sequence (aircraft_code_sequence VARCHAR2, aircraft_code VARCHAR2)
CREATE TABLE ground_service (city_code CLOB, airport_code CLOB, transport_type CLOB, ground_fare NUMBER)
CREATE TABLE aircraft (aircraft_code VARCHAR2, aircraft_description VARCHAR2, manufacturer VARCHAR2, basic_type VARCHAR2, engines NUMBER, propulsion VARCHAR2, wide_body VARCHAR2, wing_span NUMBER, length NUMBER, weight NUMBER, capacity NUMBER, pay_load NUMBER, cruising_speed NUMBER, range_miles NUMBER, pressurized VARCHAR2)
CREATE TABLE city (city_code VARCHAR2, city_name VARCHAR2, state_code VARCHAR2, country_name VARCHAR2, time_zone_code VARCHAR2)
CREATE TABLE food_service (meal_code CLOB, meal_number NUMBER, compartment CLOB, meal_description VARCHAR2)
CREATE TABLE code_description (code VARCHAR2, description CLOB)
CREATE TABLE flight_leg (flight_id NUMBER, leg_number NUMBER, leg_flight NUMBER)
CREATE TABLE fare (fare_id NUMBER, from_airport VARCHAR2, to_airport VARCHAR2, fare_basis_code CLOB, fare_airline CLOB, restriction_code CLOB, one_direction_cost NUMBER, round_trip_cost NUMBER, round_trip_required VARCHAR2)
CREATE TABLE dual_carrier (main_airline VARCHAR2, low_flight_number NUMBER, high_flight_number NUMBER, dual_airline VARCHAR2, service_name CLOB)
CREATE TABLE days (days_code VARCHAR2, day_name VARCHAR2)
CREATE TABLE state (state_code CLOB, state_name CLOB, country_name CLOB)
CREATE TABLE airport_service (city_code VARCHAR2, airport_code VARCHAR2, miles_distant NUMBER, direction VARCHAR2, minutes_distant NUMBER)
CREATE TABLE class_of_service (booking_class VARCHAR2, rank NUMBER, class_description CLOB)
CREATE TABLE time_interval (period CLOB, begin_time NUMBER, end_time NUMBER)
CREATE TABLE date_day (month_number NUMBER, day_number NUMBER, year NUMBER, day_name VARCHAR2)
CREATE TABLE restriction (restriction_code CLOB, advance_purchase NUMBER, stopovers CLOB, saturday_stay_required CLOB, minimum_stay NUMBER, maximum_stay NUMBER, application CLOB, no_discounts CLOB)
CREATE TABLE time_zone (time_zone_code CLOB, time_zone_name CLOB, hours_from_gmt NUMBER)
CREATE TABLE flight (aircraft_code_sequence CLOB, airline_code VARCHAR2, airline_flight CLOB, arrival_time NUMBER, connections NUMBER, departure_time NUMBER, dual_carrier CLOB, flight_days CLOB, flight_id NUMBER, flight_number NUMBER, from_airport VARCHAR2, meal_code CLOB, stops NUMBER, time_elapsed NUMBER, to_airport VARCHAR2)
CREATE TABLE compartment_class (compartment VARCHAR2, class_type VARCHAR2)

please show me flights from DALLAS to DENVER
SELECT DISTINCT flight.flight_id FROM airport_service AS AIRPORT_SERVICE_0, airport_service AS AIRPORT_SERVICE_1, city AS CITY_0, city AS CITY_1, flight WHERE CITY_0.city_code = AIRPORT_SERVICE_0.city_code AND CITY_0.city_name = 'DALLAS' AND CITY_1.city_code = AIRPORT_SERVICE_1.city_code AND CITY_1.city_name = 'DENVER' AND flight.from_airport = AIRPORT_SERVICE_0.airport_code AND flight.to_airport = AIRPORT_SERVICE_1.airport_code
SELECT DISTINCT "flight"."flight_id" FROM "airport_service" "AIRPORT_SERVICE_0" JOIN "city" "CITY_0" ON "AIRPORT_SERVICE_0"."city_code" = "CITY_0"."city_code" AND "CITY_0"."city_name" = 'DALLAS' JOIN "flight" ON "AIRPORT_SERVICE_0"."airport_code" = "flight"."from_airport" JOIN "airport_service" "AIRPORT_SERVICE_1" ON "AIRPORT_SERVICE_1"."airport_code" = "flight"."to_airport" JOIN "city" "CITY_1" ON "AIRPORT_SERVICE_1"."city_code" = "CITY_1"."city_code" AND "CITY_1"."city_name" = 'DENVER'