Products Catalog

Im working in Catalog App, That Contain 3 Tables (Customer,Catalog,Orders)
Iam confused between some ways which is better?

Enter the list of products to order With 0 quantity and add slice “Order” quantity>0, then when i increase the quantity of the in the products table for some Product I will see it then in the Order Table
The advantage is that the addition is via - or + of the quantity of the product

The Other way is with Action Add Row to Another Table
From Products to Order
Disadvantage of not being able to delete a line from the order