How to find and select products on invoices through joined table
I have been searching online but can't seem to find the answer. Here it is:
I have two tables, products and orders. Since 1 product can appear on multiple orders and 1 order has multiple products, I created a third table joining the two, named 'line items'. I have populated the table 'products' with some products. Now i wish to set up a lay-out for 'orders', lets say 'create new order': when i create a new order, i wish to select products from the product table How can i do that?
1. Products (has primary key 'Products ID'): table that has products in it
2. Line items (joined table, has foreign key 'Product ID' and foreign key 'Order ID'): so this table has no data yet
3. Orders (has primary key 'Order ID'): table that has no data yet
A portal i created doesnt show anything. Please be aware that i'm trying to CREATE orders, so there are NO orders in my orders table, there are ONLY products. The point is to CREATE orders through a filemaker layout. So i'm basically trying to create a connection, while in the current situation there is none yet. On the internet i find dozens of examples like here: http://www.lynda.com/FileMaker-Pro-tutorials/Understanding-portals/83839/88089-4.html that do almost the same, but in this case, there are already orders in the system. The only thing they do is link order with products that are ordered already.
Thanks for your help
See picture for my database.