As someone not versed in Mongo or anything similar, what is the alternative? A large array of docs that has to be loaded in to memory to work with?
> The example is that if you have 10 rakes in the stores,
> you can only sell 10 rakes. The approach that is taken
> is quite nice, by simulating the notion of having a
> document per each of the rakes in the store and allowing
> users to place them in their cart.
And with current amounts of RAM on servers there would be no problems even if you have tens of millions of items.
You could have a list inside a single document.
One would subtract product from amout field in products table to set new inventory level. A new order document gets created with all information needed to describe an order. Fields like total, subtotal, date would sit at the root level and line items with product descriptions and prices would be embedded as an array of objects. Then a user object with user_id, name address would be embedded.
Dealing with documents is a different but being able to contain the entire dataset with some relations is nice.