mysql - SQL Join 2个表并得到各自的答案

Question

这是我的 SQL Fiddle

我有像这样的主表

CREATE TABLE master (id int, name varchar(25), origin int, destination int);
INSERT INTO master (id, name, origin, destination) VALUES (1, 'Alpha', 1,2);
INSERT INTO master (id, name, origin, destination) VALUES (2, 'Beta', 3,4);

和机场表一样

CREATE TABLE airport (id int, name varchar(25));
INSERT INTO airport (id, name) VALUES (1, 'Chennai');
INSERT INTO airport (id, name) VALUES (2, 'Delhi');
INSERT INTO airport (id, name) VALUES (3, 'Goa');
INSERT INTO airport (id, name) VALUES (4, 'Mumbai');

我试过像这样使用这个sql查询

select master.id, master.name, master.origin,master.destination from  master
INNER JOIN airport ON master.origin=airport.id

但我只得到这个作为答案

id  name    origin  destination
1   Alpha   1   2
2   Beta    3   4

我怎么会这样

id  name    origin  destination
1   Alpha   Chennai Delhi
2   Beta    Goa     Mumbai

Answer 1

您需要两个连接:

select m.id, m.name, ao.name as origin, ad.name as destination
from master m join
     airport ao 
     on m.origin = ao.id join
     airport ad
     on m.destination = ad.id;

注意使用表别名来区分两个表。这些还有助于更轻松地编写和读取查询。