mysql - 如何编写查询来获取主键名称

Question

表结构:

Location
--------------
location_id   name
1            Location1
2            Location2
3            Location3

Tour_available
--------------
tour_available_id     from_location    to_location
1                         2               3
2                         1               2 
3                         2               1

上表中的from_location和to_location是外键(这是Location表中的主键)

我想要输出为:

Expected output
--------------
from_location    to_location
Location2         Location3
Location1         Location2
Location2         Location1

Answer 1

select FL.name as frm_location, TL.name as t_location 
  from Tour_available as TA INNER JOIN Location as FL ON (FL.location_id = TA.from_location) 
    INNER JOIN Location as TL ON (TL.location_id = TA.to_location);