Rails order by association field

I have the following models

class User
  attr_accesible :first_name, :phone_number
  has_one :user_extension
end

class UserExtension
  attr_accessible :company, :user_id
  belongs_to :user
end

I have table which contains all users. And I need to sort this table by first_name, phone_number, company. With first_name, phone_number I don't have any problems, order works fine, in example

@users = User.order("first_name desc")

, but I also need sort by company and don't know how to do it.

And I can get company name by this way

@user.user_extension.company

So i have troubles with sql, which will gave me all users ordered by company. DB: PostgreSQL. Thanks.

Edit:

I should provide more information about this models.

create_table "user_extensions", :force => true do |t|
  t.integer  "user_id"
  t.string   "company"
end

create_table "users", :force => true do |t|
  t.string   "first_name"
  t.string   "phone_number" 
end

Also, I tried use join

User.joins(:user_extension).order("user_extension.company desc")

and what i get

 User Load (1.6ms)  SELECT "users".* FROM "users" INNER JOIN "user_extensions" ON "user_extensions"."user_id" = "users"."id" ORDER BY user_extension.company desc
PG::Error: ERROR:  relation "user_extensions" does not exist

on

User.includes(:user_extension).order("user_extension.company desc")

i also get

PG::Error: ERROR:  relation "user_extensions" does not exist

Resolved Have problems with my bd, all joins works fine.

Try this:

@users = User.includes(:user_extension).order("user_extensions.company desc")

I think you need at order: user_extensions, not user_extension

Merge can make the query smaller/saner-looking, and it benchmarked faster for me in Rails 4.x:

@users = User.joins(:user_extension).merge(UserExtension.order(company: :desc))

@users = User.order("user_extension.company desc") should work fine.

Old topic, and perhaps off topic, but I needed this. FWIW:

Order by association field

User.includes(:user_extension).order('user_extensions.company ASC')

Lets make it more interesting, create more associations.

Order by the associations two levels deep.

User.includes(user_extension: :company).order('companies.name ASC')

Order by the associations three levels deep.

User.includes(user_extension: { company: :guilds }).order('guilds.secret_knock ASC')

Maybe too late but I ran into a similar issue and this is how I implement it:

scope :sort_by_company, ->{
    joins(:user_extension).order(UserExtension.arel_table[:company].lower.desc)
  }

The code above should be placed within the user model.

Hope it can help! 