如何创建此存储过程？

Question

我想创建一个存储过程，使我能够知道以西班牙为目的地的预计飞行时间（进来的机场在西班牙）。 我有下表：

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));

我该如何处理？ 如何将FLIGHT_PLAN的incomming_airport字段与AIRPORT代码FLIGHT_PLAN在一起，然后在CITY编写代码并在COUNTRY编写代码？

我应该使用外键还是什么？

Answer 1

您可以使用以下方式链接表格

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'

注意：Oracle是区分大小写的，因此请注意西班牙的拼写或使用

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')

如果您知道西班牙的代码，则可以在子选择中省略JOIN并直接添加WHERE ct.country_code = 42

如果结果中需要机场的名称和城市，则必须再次加入主要查询机场和城市：

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')