DMZ 1.7.1 (DataMapper OverZealous Edition)

[eluser]WanWizard[/eluser]
DMZ determines the names used in the query from the names of the tables, and the relationships defined. The use of the order_user table indicates DMZ sees a many_to_many relationship between user and order.

You need these relations to be defined:
Order must have a has_one to User, User must have a has_many to order.
Order must have a has_many (or a has_one) to Order_album, Order_album must have a has_one to Order
Order_album must have a has_one to Album, Album must have a has_many to Order_album.