SQL连接多个外部ID

Question

我有两个桌子。

tbl_cities：

Id, Name
---------
1  | Paris
2  | London
3  | Amsterdam
4  | Mumbai

tbl_journeys：

from_id, to_id, Journey_date
---------------------------------
1     |    2   |  1 Mar 2019
2     |    1   |  1 Mar 2019
3     |    1   |  3 Mar 2019

产生这样的输出的SQL是什么：

 City_From_Name, City_To,Name, Journey_Date
------------------------------------------------
Paris          | London       | 1 Mar 2019
London         | Paris        | 1 Mar 2019
Amsterdam      | London       | 3 Mar 2019

Answer 1

与tbl_cities两次

select b.name as City_From_Name,b1.name as City_To,Name,journey_date
from 
tbl_journeys a inner join tbl_cities b on a.from_id=b.id
inner join tbl_cities b1 on a.to_id=b1.id

Answer 2

请尝试这个。

Select B.Name As City_From_Name, C.Name As City_To_Name, A.Journey_Date from tbl_journeys A
LEFT JOIN  tbl_cities B
ON B.id = A.From_id
LEFT JOIN  tbl_cities  C
ON C.id = A.To_id

Answer 3

SELECT c1.Name City_From_Name , c2.Name City_To,Name, j.Journey_date Journey_Date
FROM tbl_journeys j
       INNER JOIN tbl_cities c1 ON c1.Id = j.from_id
       INNER JOIN tbl_cities c2 ON c2.Id = j.to_id

Answer 4

尝试一下

从tbl_cities，tbl_journeys中选择tbl_cities.Name作为“ City_from_Name”，tbl_journeys.to_Id作为“ City_to_Name”，tbl_journeys.Journeys.date，其中tbl_cities.Id = tbl_journeys.from_id;