sample_migration.rb

migration 1, :create_people_table do
  up do
    puts "up"
    create_table :people do
      column :id,   Integer, :serial => true
      column :name, String, :size => 50
      column :age,  Integer
    end
  end
  down do
    drop_table :people
  end
end

migration 2, :add_extra_props_people do
  up do
    modify_table :people do
      add_column :extra, String, :nullable? => true
    end
  end

  down do
    modify_table :people do
      drop_column :extra
    end
  end
end

migration 3, :rename_age_to_birthyear do
  up do
    execute 'ALTER TABLE people CHANGE COLUMN `age` `birthyear` INTEGER DEFAULT 0'
  end
  down do
    execute 'ALTER TABLE people CHANGE COLUMN `birthyear` `age` INTEGER DEFAULT 0'
  end
end