Try this:
> person_id = 1
> person = Person.includes(:favorite_car, :business_car, :home_car).where("people.id" = ?", person_id).references(:favorites_car, :business_car, :home_car)
> person[0].favorite_car
app/models/person.rb
class Person < ActiveRecord::Base
# columns: id, name, favorite_car_id, business_car_id, home_car_id
belongs_to :favorite_car, class_name: 'Car'
belongs_to :business_car, class_name: 'Car'
belongs_to :home_car, class_name: 'Car'
end
app/models/car.rb
class Car < ActiveRecord::Base
# columns: id, name
has_many :people
end
Proof that this works:
> Person.all
Person Load (0.3ms) SELECT "people".* FROM "people"
=> #<ActiveRecord::Relation [#<Person id: 1, favorite_car_id: 1, business_car_id: 2, home_car_id: 3, name: "Frankie", created_at: "2014-02-18 21:51:58", updated_at: "2014-02-18 21:53:34">]>
> Car.all
Car Load (0.3ms) SELECT "cars".* FROM "cars"
=> #<ActiveRecord::Relation [#<Car id: 1, name: "Mazda", created_at: "2014-02-18 21:52:16", updated_at: "2014-02-18 21:52:16">, #<Car id: 2, name: "Honda", created_at: "2014-02-18 21:52:20", updated_at: "2014-02-18 21:52:20">, #<Car id: 3, name: "BMW", created_at: "2014-02-18 21:52:24", updated_at: "2014-02-18 21:52:24">]>
> Person.includes(:favorite_car, :business_car, :home_car).where("people.id = ?", 1).references(:favorite_car, :business_car, :home_car)
SQL (0.4ms) SELECT "people"."id" AS t0_r0, "people"."favorite_car_id" AS t0_r1, "people"."business_car_id" AS t0_r2, "people"."home_car_id" AS t0_r3, "people"."name" AS t0_r4, "people"."created_at" AS t0_r5, "people"."updated_at" AS t0_r6, "cars"."id" AS t1_r0, "cars"."name" AS t1_r1, "cars"."created_at" AS t1_r2, "cars"."updated_at" AS t1_r3, "business_cars_people"."id" AS t2_r0, "business_cars_people"."name" AS t2_r1, "business_cars_people"."created_at" AS t2_r2, "business_cars_people"."updated_at" AS t2_r3, "home_cars_people"."id" AS t3_r0, "home_cars_people"."name" AS t3_r1, "home_cars_people"."created_at" AS t3_r2, "home_cars_people"."updated_at" AS t3_r3 FROM "people" LEFT OUTER JOIN "cars" ON "cars"."id" = "people"."favorite_car_id" LEFT OUTER JOIN "cars" "business_cars_people" ON "business_cars_people"."id" = "people"."business_car_id" LEFT OUTER JOIN "cars" "home_cars_people" ON "home_cars_people"."id" = "people"."home_car_id" WHERE (people.id = 1)
=> #<ActiveRecord::Relation [#<Person id: 1, favorite_car_id: 1, business_car_id: 2, home_car_id: 3, name: "Frankie", created_at: "2014-02-18 21:51:58", updated_at: "2014-02-18 21:53:34">]>
Important Note: Rails will automagically use people
as the plural of person
. So when you create a Person
model, it will create a people
database table.