I am trying to forget about tables and think about objects, i am a bit confused about this i appreciate your clarification, this is about relations between orders and invoices:
In shopping cart user should be able to add multiple items but finally when order should be created, this is better to create separate record for each order item because some items may have recurring invoices and some items may not, or may be even some items are included for free like bonus etc. So to manage recurring invoices better to have separate order record for each item however all items were in one cart. But for these all order items there should be one initial invoice on first purchase (however for next recurring there might be separate invoice for each item) so at this time the relation from order to invoice at first time is many to one: Some order items have one invoice because purchased together at the same time and payment should be done once for all items. But on recurring invoices, the relation from order to invoice would be one to many, because order done once and has several recurring invoices, so thinking as object the relation between order to invoice is many to many? Right? I appreciate your advice.