เที่ยวบินใดจากดัลลาสไปฮูสตันในวันอาทิตย์ไม่จำเป็นต้องใช้ตารางทั้งหมด
what flights from DALLAS to HOUSTON on sundayIt is not neccessary to use all the tables.
 food_service:  meal_code [ text]  meal_number [ int]  compartment [ text]  meal_description [ varchar] 
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, date_day, days, flight WHERE (CITY_1.city_code = AIRPORT_SERVICE_1.city_code AND CITY_1.city_name = 'HOUSTON' AND date_day.day_number = 27 AND date_day.month_number = 8 AND date_day.year = 1991 AND days.day_name = date_day.day_name AND flight.flight_days = days.days_code AND flight.to_airport = AIRPORT_SERVICE_1.airport_code) AND CITY_0.city_code = AIRPORT_SERVICE_0.city_code AND CITY_0.city_name = 'DALLAS' AND flight.from_airport = AIRPORT_SERVICE_0.airport_code