#215 Advanced Queries in Rails 3

Product.cheap.to_sql
(Category.joins(:products) & Product.cheap).to_sql
Category.with_cheap_products.to_sql
p = Product.discontinued.build
p.discontinued
t = Product.arel_table
t[:price].eq(2.99)
t[:name].matches("%catan").to_sql
Product.where(t[:price].eq(2.99).or(t[:name].matches("%catan")))

scope :discontinued, where(:discontinued => true)

def self.cheaper_than(price)
  where("products.price < ?", price)
end

scope :cheap, cheaper_than(5)

scope :with_cheap_products, joins(:products) & Product.cheap