chapter03code.txt

require 'rubygems'
require_gem 'activerecord'

if ARGV[0] =~ /VERSION=\d+/
  version = ARGV[0].split('=')[1].to_i
else
  version = nil
end

@logger = Logger.new $stderr
ActiveRecord::Base.logger = @logger
ActiveRecord::Base.colorize_logging = false

@config = YAML.load_file(File.join(File.dirname(__FILE__), 'database.yml'))
ActiveRecord::Base.establish_connection(@config["development"])
ActiveRecord::Migrator.migrate("", version)

class CreateUsersTable < ActiveRecord::Migration
    def self.up
    end

    def self.down
    end
end

# Script to create the first version of a Cows table
def self.up
    create_table :cows do |t|
        t.column :name, :string
        t.column :breed, :string
        t.column :born_on, :datetime
        t.column :milkable, :boolean
    end
end

mysql> show tables;
Empty set (0.12 sec)

mysql> describe cows;

mysql> show tables;

mysql> select * from schema_info;

def self.down
    drop_table :cows
end

mysql> show tables;

def self.up
    add_column :cows, :farmer_id, :integer
end

def self.down
    remove_column :cows, :farmer_id
end

mysql> describe cows;

rename_column :cows, :born_on, :created_on

change_column :address, :postal_code, :string

add_index :cows, :farmer_id, :name => "index_on_cows_for_farmers"
add_index :ownerships, [:farmer_id, :tractor_id], :unique => true

remove_index :ownerships, :column => [:farmer_id, :tractor_id]

remove_index :cows, :name => "index_on_cows_for_farmers"

def self.up
  add_column :orders, :total, :decimal

  orders = Order.find(:all)
  orders.each do |order|
    subtotal = 0
    order.line_items.each do |line_item|
      subtotal += line_item.quantity * line_item.price
    end
    order.total = subtotal
  end
end

def self.down
  remove_column :orders, :total
end

def self.up
  add_column :orders, :total, :decimal
  ActiveRecord.execute("UPDATE orders LEFT OUTER JOIN line_items
    SET orders.total=SUM(line_items.quantity * line_items.price) ON
    orders.id=line_items.order_id")
end 

def self.down
  remove_column :orders, :total
end