How to create this stored procedure?

Question

I want to create a stored procedure that allows me to know the estimated time of the flights with Spain as destination (the incoming airport is in Spain). And I have the following tables:

FLIGHT_PLAN(plan_number NUMBER, outgoing_airport NUMBER, estimated_flight_time NUMBER, incoming_airport NUMBER);

AIRPORT (code NUMBER, name VARCHAR(20), city_code NUMBER);

CITY (code NUMBER,name VARCHAR(20),country_code NUMBER);

COUNTRY (code NUMBER, name VARCHAR(20));

How can I go through this? How can I chain the incomming_airport field in FLIGHT_PLAN with code in AIRPORT and then code in CITY and code in COUNTRY ?

Should I use foreign keys or what?

Answer 1

You can link the tables up using

FROM COUNTRY C
inner join CITY I on I.country_code = C.code
inner join AIRPORT A on A.city_code = I.code
inner join FLIGHT_PLAN F on F.incoming_airport = A.code
WHERE C.name = 'Spain'

Note: Oracle is ase sensitive so watch the spelling of Spain, or use

WHERE UPPER(C.name) = 'SPAIN'

Answer 2

SELECT plan_number, 
       outgoing_airport, 
       incoming_airport,
       estimated_flight_time
FROM flight_plan 
WHERE incoming_airport IN (SELECT ap.code
                           FROM airport ap 
                             JOIN city ct ON ct.code = ap.city_code
                             JOIN country co ON co.code = ct.country_code
                           WHERE co.name = 'Spain')

If you know the code for spain, you can leave out the JOIN in the sub-select and directly add WHERE ct.country_code = 42

If you need the name and city of the airport in the result, you'll have to join the main query agains airport and city:

SELECT fp.plan_number, 
       fp.estimated_flight_time,
       fp.outgoing_airport, 
       out_ap.name as outgoing_airport_name,
       out_city.name as outgoing_city_name,
       fp.incoming_airport,
       in_ap.name as incoming_airport_name,
       in_city.name as incoming_city_name
FROM flight_plan fp 
  JOIN airport in_ap ON in_ap.code = fp.incoming_airport
  JOIN city in_city ON in_city.code = in_ap.city_code
  JOIN airport out_ap ON out_ap.code = fp.outgoing_airport
  JOIN city out_city ON out_city.code = out_ap.city_code
WHERE incoming_airport IN (SELECT ap.code
                           FROM airport ap 
                             JOIN city ct ON ct.code = ap.city_code
                             JOIN country co ON co.code = ct.country_code
                           WHERE co.name = 'Spain')