Question

我的架构如下：

airports表包含机场名称。它的主键是整数id。
flights表格包含航班数据。它有两个外键departure_airport_id和arrival_airport_id

我想在航班上获取出发和到达机场的名称。现在我的SQL如下：

SELECT name AS departure_airport, name AS arrival_airport FROM flights, airports WHERE departure_airport_id = airports.id OR arrival_airport_id = airports.id

我可以看到这是多么含糊不清，因为数据库无法通过departure_airport知道departure_airport_id我的意思是arrival_airport和{{1}}的名称我是指'arrival_airport_id'的名称，但在航班记录上获取两个机场名称的正确方法是什么？

Answer 1

从飞往机场桌的航班加入两次，如下：

SELECT dep.name AS departure_airport, arr.name AS arrival_airport 
FROM flights f
    JOIN airports dep ON f.departure_airport_id = dep.id 
    JOIN airports arr ON f.arrival_airport_id = arr.id

Answer 2

    SELECT departure_airport.name AS departure_airport, 
           arrival_airport.name AS arrival_airport 
      FROM flights
INNER JOIN airports departure_airport
        ON departure_airport.id = flights.departure_airport_id
INNER JOIN airports arrival_airport
        ON arrival_airport.id = flights.arrival_airport_id

如果使用不同的别名，可以多次连接到表格。

Answer 3

SELECT depart.name AS departure_airport, arr.name AS arrival_airport 
FROM flights, airports arr,airports depart 
WHERE departure_airport_id = depart.id and
arrival_airport_id = arr.id

获取相同类型的两个数据库列的关联名称

3 个答案: