红宝石onrails加入表

Question

我想以轨道方式加入我的表。

这是SQL查询

SELECT * FROM `ads` left join `state` ON ads.state_id = states.id 

Answer 1

Rails guides是你的朋友=）

Answer 2

http://api.rubyonrails.org/classes/ActiveRecord/Base.html

Student.joins(:schools).where(:schools => { :type => 'public' }) 
Student.joins(:schools).where('schools.type' => 'public') 

或者Rails ActiveRecord :joins with LEFT JOIN instead of INNER JOIN：

User.find(:all, :limit => 10, 
     :joins => "LEFT JOIN `user_points` ON user_points.user_id = users.id" , 
     :select => "users.*, count(user_points.id)", :group => 
     "user_points.user_id")