Question

我有

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);

还有机场桌

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');

我尝试使用

这样的SQL查询

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

但是我只能得到这个答案

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

您需要两个联接：

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;

请注意使用表别名来区分两个表。这些也有助于简化查询的编写和读取。

Answer 2

您可以尝试此查询，希望您能找到想要的答案。

查询：

 SELECT master.id,
       master.name,
       master.destination                       AS destination,
       (SELECT airport.name
        FROM   airport
        WHERE  airport.id = master.origin)      AS origin,
       (SELECT .airport.name
        FROM   airport
        WHERE  airport.id = master.destination) AS destination
FROM   master

SQL联接2个表并获得各自的答案

2 个答案: