How can I do a LEFT OUTER JOIN using Rails ActiveRecord?

Question

I don\'t have any ideas. Could you give me any clues (like reference sites). Any help will be appreciated.

Model1: GROUP         


        

Answer 1

Use has_and_belongs_to_many if you just need to link users to groups. Use has_many :through if you need to store additional membership information.

Example:

class User < ActiveRecord::Base
  has_and_belongs_to_many :groups
end

class Group < ActiveRecord::Base
  has_and_belongs_to_many :users      
end