Guest user orders in e commerece website

I think this is the appropriate place for this kind of post. So I am building an ecommerece website. I have users table and the orders table. Each user can have many orders.

I add registered user orders in the shopping cart and then they proceed to checkout.

But if user is guest user . He just comes and place order.

How can I get orders of this guest user . Which criteria should i use to filter out orders of this guest user.

This is more of an implementation detail question.

Any suggestions will be much appreciated.

I guess most systems work with the email address. So if I place an order somewhere without an account, I usually have to enter my email address for the invoice and order confirmation. When I then create an account at a later point in time, most systems show me the orders I made as a guest because they look them up by email address.

Thanks for your reply. I get that work flow . But i am talking about getting the guest user orders in the shopping cart. The work flow is user comes to the site. Add few items in the shopping cart and then click on shopping cart button. The shopping cart view opens and it has all the guest users orders in it. So how can i get these orders.

Then you would store the product ID and quantity in the user session.