Portal from one-to-many via a join to another one-to-many
I have three tables. A one-to-many, a join table, and another one-to-many table. I want to view and edit records on one of the one-to-many tables with the other one-to-many. When I place the a portal from the join table on my layout the records are blank.
I want to pick a value from the portal, and then add a value to the portal record. What field do I use on the portal as a link... does it need to be a global? If so, what do I put in the global field. Global fields intimidate me. Despite reviewing examples I just don't seem to get it.
I have no problem with portals coming from a child on a parent layout... It's when that join table is involved that I can't get the portal to work.
What are the limited number of field elements required to make such a relationship work? I assume you need multiple foreign keys in the join table, the field you want to use as your drop-down, and the field you want to add a value to.
(additional fields if you want to add values)
The other two tables both have primary keys linked to the jointable via the foregin keys. What else is required that I'm missing to make this work?