ruby-on-rails - 如何将参数传递给 LEFT JOIN？

Question

** 为更好理解而编辑**

** 编辑重命名为文档 **

我想获取给定用户的所有带有投票记录的用户文档记录，如果该用户未对某些文档记录进行投票，我仍然希望获取所有没有投票的文档记录。 例如:

+------------+--------------+------+
|document.par1|document.par2| vote |
+------------+--------------+------+
|    2       | z            | y    |
|    3       | w            | NULL |
|    4       | x            | NULL |
+------------+--------------+------+

如果我尝试在 Ruby on Rails 上:

我。第一次尝试:

Document.
   joins("LEFT JOIN `votes` ON `votes`.`v_id` = `document`.`id` AND `votes`.`giver_id` = ?", user_id).
   where('document.creator_id = ?', user_id, .....).
   select('votes.*', `document.param1')

我得到了这个错误:

RuntimeError in UserDocumentsController#show

unknown class: Fixnum

二。第二次尝试:

Document.
   joins("LEFT JOIN `votes` ON `votes`.`v_id` = `document`.`id`").
   where('document.creator_id = ? AND `votes`.`giver_id` = ?', user_id, user_id, .....).
   select('votes.*', `document.param1')

仅返回有投票的记录:

+-------------+-------------+------+
|document.par1|document.par2| vote |
+-------------+-------------+------+
|    2        | z           | y    |
+-------------+-------------+------+

所以少了2条记录..

** 已更新，此解决方案有效 **

三。我的第三次尝试，感谢 Mischa 的帮助:

Document.
   joins("LEFT JOIN `votes` ON `votes`.`v_id` = `document`.`id`").
   where('document.creator_id = ? AND (`votes`.`giver_id` = ? OR  `votes`.`giver_id` IS NULL)', user_id, user_id).
   select('votes.*', `document.param1')

+-------------+-------------+------+
|document.par1|document.par2| vote |
+-------------+-------------+------+
|    2        | z           | y    |
|    3        | w           | NULL |
|    4        | x           | NULL |
+-------------+-------------+------+

Answer 1

这将为您提供所需的结果集:

Document.
   joins("LEFT JOIN `votes` ON `votes`.`v_id` = `document`.`id`").
   where('document.creator_id = ? AND (`votes`.`giver_id` = ? OR  `votes`.`giver_id` IS NULL)', user_id, user_id).
   select('votes.*', `document.param1')