How to calculate the amount of materials and where to store it?

Question

Laravel

How to count the number of materials and where to write it down with such a database structure?
StoreOrder
-> store_id
-> type = inbound/outbound
StoreOrderItem
-> store_order_id
-> material_id
-> price
-> quantity
Material
-> name
-> position

Answer 1

-> quantity is the same as the number of materials in the order