如何在rails find中执行Left join

我有这个

User.joins(:notifications).joins(:company_users).joins(:role_users).where("notifications.id = ? AND role_users.role_id != '1' AND (company_users.company_id = ? OR users.company_id = ?)", notification.id, p.company_id, p.company_id) 

=> []

哪个产生这个sql

 SELECT `users`.* FROM `users` INNER JOIN `subscriptions` ON `users`.`id` = `subscriptions`.`user_id` INNER JOIN `notifications` ON `notifications`.`id` = `subscriptions`.`notification_id` INNER JOIN `company_users` ON `company_users`.`user_id` = `users`.`id` INNER JOIN `role_users` ON `role_users`.`user_id` = `users`.`id` WHERE (notifications.id = 1 AND role_users.role_id != '1' AND (company_users.compcany_id = 67 OR users.company_id = 67)) 

问题是我需要在company_users上保持联接并且不确定如何在rails中实现这一点

我知道我可以用find_by_sql做到这一点,我听说这不是真的像……任何想法

解决了

 User.joins(:notifications).joins("LEFT JOIN `company_users` ON `company_users`.`user_id` = `users`.`id`").joins(:role_users).where("notifications.id = ? AND role_users.role_id != '1' AND (company_users.company_id = ? OR users.company_id = ?)", notification.id, p.company_id, p.company_id) 

class User

  has_many :friends, :foreign_key=>"u_from",:class_name=>"Friend" 

结束

class Friend

  belongs_to :user 

结束

friends = user.friends.where(:u_req_status => 2).joins(“LEFT OUTER JOIN users ON users.u_id = friends.u_to”)。select(“friend_id,u_from,u_to,u_first_name,u_last_name,u_email,u_fbid, u_twtid,u_picture_url,u_quote“)