SQL Select语句具有从同一表中获取的两个外键

Question

create table A ( 
    cityID int, 
    cityname nvarchar(30), 
    primary key (cityID)
)

create table b (
    travelID int, 
    fromcityID int, 
    tocityID int, 
    primary key (travelID),
    foreign key (fromcityID) references A (cityID),
    foreign key (tocityID) references A (cityID)
)

insert into A values(1,'amman');
insert into A values(2,'Irbid');

insert into B values(1,1,1)
insert into B values(2,1,2)
insert into B values(3,2,1)
insert into B values(4,2,2)



select travelID, a.cityname,a.cityname  from A, b where ????

我应该在select语句中写些什么来查看城市名称而不是城市ID？

Answer 1

尝试以下查询：

SELECT a.cityname,c.cityname from B b
JOIN A a ON b.fromcityID=a.cityID
JOIN A c ON b.tocityID=c.cityID

我使用别名来避免查询中的歧义.............