CODEWITHSUNDEEP
ruby-on-rails
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Reputation: 5728

Querying many to many relation in Ruby on Rails

Let's say I have an app where users could rate books. Tables are users(id), books(id) and rating(user_id, book_id, value). I've made these models

class Rating < ActiveRecord::Base
  belongs_to :user
  belongs_to :book
end

class User < ActiveRecord::Base
  has_many :ratings
end

class Book < ActiveRecord::Base
  has_many :ratings
end

I want to get a list of all (both rated and unrated) books with their ratings made by current user. It's easy in SQL with outer join but I can't figure out a way to do it in Rails 3.

Upvotes: 0

Views: 1153

Answers (2)

Aditya Sanghi
Aditya Sanghi

Reputation: 13433

it's quite simple in rails too. You probably should add a relationship in user with books as well.

class User < ActiveRecord::Base
  has_many :ratings
  has_many :users, :through => :ratings
end

current_user.books.includes(:ratings).all

should work.

Upvotes: 0

David Sulc
David Sulc

Reputation: 25994

According to LEFT OUTER joins in Rails 3 you'll have to specify the outer join in SQL...

Upvotes: 1

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