从控制台加入两个表

Question

我有以下 tables...

class QuestionEvent < ActiveRecord::Base
...
  belongs_to :recipient, :class_name => "User", :foreign_key => "recipient_id"

...这让我可以...

2.1.5 :001 > qe = QuestionEvent.find 475282
  QuestionEvent Load (0.4ms)  SELECT `question_events`.* FROM `question_events` WHERE `question_events`.`id` = 475282 LIMIT 1
 => #<QuestionEvent id: 475282, question_id: 112307, initiated_by_id: 17, recipient_id: 10696, "2013-03-13 13:08:14", updated_at: "2013-03-13 13:08:14", updated_question_values: nil, changed_tag: nil>
2.1.5 :002 > qe.recipient
  User Load (0.3ms)  SELECT `users`.* FROM `users` WHERE `users`.`id` = 10696 LIMIT 1
 => nil

我正在寻找的是一个查询，我可以从控制台运行向我显示 recipients 为零的所有 QuestionEvents。在上面的例子中，有一个 recipient_id，但是，那个 id 不在 User table.

我试过 QuestionEvent.includes(:recipient).where("recipient_id", nil) 但没有雪茄。

Answer 1

尝试：

QuestionEvent.where("question_events.recipient_id NOT IN (?)", User.pluck(:id))

Answer 2

我们可以使用 2 个查询

user_ids = User.pluck(:id)
QuestionEvent.where("recipient_id NOT IN (?)", user_ids)

从控制台加入两个表

Join on two tables from the console

ruby-on-rails

rails-console