php - mysql 从 users 表中连续加入 2 个 user_ids

Question

有2张桌子：

orders:
id   requester_id   supplyer_id  status
1    423            1           reserved
2    500            1           supplied
3    222            2           reserved
...

users
id    username  register_date
1     admin     2012-01-01
2     smith     2013-01-01
...
423   John      2012-10-11
500   Doe       2012-12-11
222   name      2012-10-13 
...

我想加入这两个表并得到这个结果

id  requester_username   supplier_username  status
1   John                 admin              reserved
2   Doe                  admin              supplied
3   name                 smith              reserved

我实际上可以使用活动记录加入这些表，例如：

$this->db->select('orders.*,users.username')
   ->from('orders')
   ->join('users','users.id = orders.requester_id')
   ->get()->result();

但我不知道如何同时获得supplier username。

Answer 1

尝试添加第二个 JOIN：

$this->db->select('orders.*,requesters.username,suppliers.username')
   ->from('orders')
   ->join('users AS requesters', 'requesters.id = orders.requester_id')
   ->join('users AS suppliers',  'suppliers.id  = orders.supplier_id')
   ->get()->result();

Answer 2

在 MySql 你的查询应该像 -

Select a.id, b.username, c.username, a.status
from orders a, users b, users c
where
a.requester_id = b.id 
And
a.supplyer_id = c.id

谢谢