如何使用left-join编写mySQL来解决这类问题？

Question

如何使用左连接构造解决此问题的mySQL查询？

Feed Table
-id
-lastpost_id (The id of the user from USER TABLE who last posted)
-firstpost_id (The id of the user from USER TABLE who first posted)

User Table
-id
-name

我想要一张那样的桌子。

Result 
-id
-lastpost_id
-lastpost_name
-firstpost_id
-firstpost_name

Answer 1

select *, a.name as lastpost_name, b.name as firstpost_name from Feed f 
      left join user a on f.lastpost_id=a.id 
      left join user b on f.firstpost_id=b.id

诀窍是使用左连接，然后将表别名为a或b。这样，您可以对同一个表进行多个连接