mysql - 如何在mysql中使用内部查询获取源城市和目的地城市名称

Question

table_cities - city_id, city_name
table_booking - booking_id, source_city_id, destination_city_id

我想获取 Booking_id |来源城市名称 |结果是目的地城市名称。

我正在尝试这个:

SELECT * FROM table_bookings
    INNER JOIN table_cities
        ON table_bookings.source_city_id = table_cities.city_id
    INNER JOIN table_cities
        ON table_bookings.destination_city_id = table_cities.city_id;

但它给出的不是唯一的表/别名:'table_cities'

有人可以帮忙吗？

Answer 1

您需要为查询添加别名，这是因为您两次加入表 table_bookings 并选择 * 表名称不明确，因此您需要添加加入后使用别名以使其清晰:

SELECT
         table_bookings.Booking_id,
         sourceCities.source_city_name,
         destinationCities.destination_city_name
    FROM table_bookings
    INNER JOIN table_cities AS sourceCities
        ON table_bookings.source_city_id = table_cities.city_id
    INNER JOIN table_cities AS destinationCities
        ON table_bookings.destination_city_id = table_cities.city_id;