独立加入两列

Question

假设我有一个包含两列的table_1：buyer_id和seller_id。我有另一个表table_2，有两列：person_id，city。我的目标是一个包含四列的表格：buyer_id，buyer_city，seller_id，seller_city。

我知道我可以在那里找到像

这样的东西

SELECT a.*, b.city as buyer_city FROM
table_1 a
JOIN table_2 b ON (a.buyer_id = b.person_id)

然后我可以再做第二次查询以获得卖家。但有没有办法在单个查询中获得我想要的东西？

Answer 1

加入SELECT a.*, buyer.city as buyer_city, seller.city as seller_city FROM table_1 a JOIN table_2 buyer ON a.buyer_id = buyer.person_id JOIN table_2 seller ON a.seller_id = seller.person_id 两次

>> A = zeros(5)

A =

     0     0     0     0     0
     0     0     0     0     0
     0     0     0     0     0
     0     0     0     0     0
     0     0     0     0     0