CODEWITHSUNDEEP
ruby-on-railsruby-on-rails-4rails-activerecord
kofran
kofran

Reputation: 13

Query from two tables active record

I'm learning Ruby on Rails, I make a very simple app. This is the schema.rb:

ActiveRecord::Schema.define(version: 20160112141616) do

  create_table "cities", force: :cascade do |t|
    t.string   "name"
    t.datetime "created_at", null: false
    t.datetime "updated_at", null: false
    t.integer  "state_id",   null: false
  end

  add_index "cities", ["state_id"], name: "index_cities_on_state_id"

  create_table "states", force: :cascade do |t|
    t.string   "name"
    t.datetime "created_at", null: false
    t.datetime "updated_at", null: false
  end

end

I loaded some states and cities. And I don't know how to make a query like this using Active Record:

SELECT cities.name, states.name FROM cities INNER JOIN states ON cities.state_id = states.id

I want to do that to print in a view, all of the cities names with their states names.

Thanks.

EDIT:

model city.rb:

class City < ActiveRecord::Base
  belongs_to :states
  validates :state_id, presence: true
end

model state.rb:

class State < ActiveRecord::Base
  has_many :cities
end

cities_controller.rb:

class CitiesController < ApplicationController
  def index
    #@cities = City.all.order(state_id: :asc)
    #@cities = State.joins(:cities).select('cities.name, states.name')
    @cities = City.joins(:states).select('cities.name, states.name')
  end

  def new
    @city = City.new
    @states = State.all.order(name: :asc)
  end

  def create
    @city = City.new(city_params)
    if @city.save(:validate=> true)
      redirect_to :back
    else
      render :new
    end
  end

  def city_params
    params.require(:city).permit(:name, :state_id)
  end
end

Upvotes: 1

Views: 1451

Answers (1)

Pavan
Pavan

Reputation: 33552

The below query will do

City.joins(:states).select("cities.name, states.name")

NameError: uninitialized constant City::States

The association name for the belongs_to should be singular, so change states to state in city.rb model

class City < ActiveRecord::Base
  belongs_to :state
  validates :state_id, presence: true
end

Upvotes: 1

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