Use case 3: Lookup list for reusable items (many-to-many)
The last use case is the list of products which are stated on the invoice. Any invoice can contain more than one product. In this example, the products are software licenses.
The name of the list is “Invoice Items” and looks like this:
As you can see, it has couple of attributes but they are not so important for this use case. The important thing is: when you add a reference to this lookup column to the “Invoices” list, you should select the check box “Allow multiple values” (marked red below).
This will allow you to add/remove items on the invoice form (when entering new invoice or updating an existing one) by rendering Add/Remove control on the Invoice form that looks like this:
The benefit for the users is to refer to the same set of items on each invoice, but also to add as many items as necessary.
Finally, here is the list of all “Invoices” columns. I have marked all our lookup columns: