Error while implementing unions in ruby ​​on rails 3.2

I created two tables in the database i.e. products and shopping_list. I gave the products a foreign key reference for shopping_list, i.e. product.shopping_list_id.

I am trying to implement joins in ruby ​​on rails, but I am getting the error

my route.rb file looks like this

Shop::Application.routes.draw do
  resources :shopping_lists do
    member do
     post 'add'
     get 'delete'
    end

    collection do
     get 'add'
     get 'joins'
     get 'list'     
     post 'get_shopping_lists'
    end
  end

  resources :shopping_lists

  # ---- Contact Routes ------

  resources :products do
    member do
     post 'add'
     get 'delete'
    end

    collection do
     get 'add'
     get 'list'  
     post 'get_products'   
    end
  end  

  resources :products

      

        
        
        
      

    

my product.rb

class Product < ActiveRecord::Base


        attr_accessible :id, :shopping_list_id, :product_name, :product_category, :quantity, :status

        # ------- ASSOCIATIONS --------

        belongs_to :shopping_list


        # ------ VALIDATIONS ------

        validates_presence_of    :id, :product_name

        validates_uniqueness_of  :id

        # -------- SCOPES ----------

        # scope :not_deleted, where("products.deleted = 0")

        # default_scope not_deleted

    end

      

        
        
        
      

    

my shopping_list.rb

class ShoppingList < ActiveRecord::Base
    attr_accessible :id, :shopping_list_name, :shopping_list_status, :total_items, :created_by, :last_updated_by

    # ------- ASSOCIATIONS --------

    has_many :products


    # ------ VALIDATIONS ------

    validates_presence_of    :id, :shopping_list_name

    validates_uniqueness_of  :id

    # -------- SCOPES ----------

    # scope :not_deleted, where("shoppinglistsqa.deleted = 0")

    # default_scope not_deleted
end

      

        
        
        
      

    

the request I am trying to implement is

select shopping_lists.shopping_list_name,shopping_lists.id,products.product_name,products.product_category
from products,shopping_lists
where shopping_lists.id=products.shopping_list_id;

      

        
        
        
      

    

Could you help me.