diff --git a/db/migrate/20130405012238_alter_bike.rb b/db/migrate/20130405012238_alter_bike.rb
new file mode 100644
index 0000000..cecfeeb
--- /dev/null
+++ b/db/migrate/20130405012238_alter_bike.rb
@@ -0,0 +1,13 @@
+class AlterBike < ActiveRecord::Migration
+  def up
+    add_column(:bikes, :shop_id, :string)
+    add_index :bikes, :shop_id, :unique => true
+    remove_index :bikes, :column => :serial_number
+  end
+
+  def down
+    remove_index :bikes, :column => :shop_id
+    remove_column(:bikes, :shop_id)
+    add_index :bikes, :serial_number, :unique => true
+  end
+end