ActiveRecord (the ORM component of Rails) is really a pretty slick little piece of equipment. Not only does it integrate seamlessly with the other parts of the Rails stack, it can be easily used on its own. I do so frequently when trying to duplicate reported bugs. Consider the following little script:

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require 'active_record'

ActiveRecord::Base.logger = Logger.new(STDERR)
ActiveRecord::Base.colorize_logging = false

ActiveRecord::Base.establish_connection(
  :adapter => "sqlite",
  :dbfile  => ":memory:"
)

ActiveRecord::Schema.define do
  create_table :foxes do |t|
    t.column :name, :string
  end

  create_table :trucks do |t|
    t.column :fox_id, :integer
    t.column :color, :string
  end
end

class Fox < ActiveRecord::Base
  has_many :trucks
end

class Truck < ActiveRecord::Base
  belongs_to :fox
end

fox = Fox.create :name => "Small"
fox.trucks.create :color => "Blue"
fox.trucks.create :color => "Orange"

puts Fox.find(1).trucks.length

The above script uses an in-memory SQLite database, so it doesn’t leave any messes around on disk. It also logs to STDERR, so I can see all the SQL that is produced, and it turns off colorized logging (because I prefer a white-background terminal and AR’s colors aren’t very friendly to that). It then defines the tables using ActiveRecord::Schema, defines the classes, adds some data, and then manipulates the data.

Nice and simple! (Note that ActiveRecord::Schema is only available in the beta gems, currently, but everything else should work with the released version of AR.)