You can't limit table occurrences, but you can limit value lists and you can limit the records shown on a layout or in a portal.
I think you are asking for a value list drawn only from people records that are identified as instructors.
Option 1 will do what you need, but also look at option 2. The second option is more flexible and can be used to pull up any number of different subgroups of the values in the table. (You could pull up a list of teaching assistants, for example.)
You may also find this demo file helpful:
Cool. I understand how to make the conditional value list thanks to your help before but I'm confused about the table occurences.
Right now I have this relationship:
Table: People-->Table: Class Registrations-->Classes
A layout of the "Classes" table contains a portal to the Table "Class Registrations" which lists records of the people who are enrolled in the class. Is it possible to make another Tab on this "Classes" table that contains people records as well except this time in the context of instructors? Or will it make it a circular relationship?
"Is it possible to make another Tab on this "Classes" table [Layout] that contains people records as well except this time in the context of instructors? Or will it make it a circular relationship?"
If you have Filemaker 11, you can place a portal to this same table occurrence, but filter the portal to exclude all records except where the people record is flagged as an Instructor.
If you don't have FileMaker 11, you can still do this, but then you need an extra table occurrence so you can set up a different relationship.
The complication with doing it as a filtered portal is that an instructor may be an instructor in some classes, but a student in another. I don't want to create a new field in class registrations that we have to mark each time as "instructor" or "student." I could do that if there is no better way.
Ideally, I'd like to make a new relationship between people and classes, that combine onto a table called "instructor assignments." Is that at all possible?
You'll need some kind of field to distinguish instructors from students. Otherwise there's no way to tell the difference. I was thinking in terms of a field in People that identified instructors, but that was before you indicated that an instructor of one class could be a student in another...
Adding a new relationship still requires that extra field or you won't be able to design a relationship that matches only to the instructor, so portal filtering is still simpler than adding another relationship.
I don't see any way to avoid adding a field to registrations for identifying the instructor.
Cool thanks for your help. I think I am going to try adding an instructor y/n field to Class registrations instead of to the People table, and then just mark people as instructor is that is their role.
Wish me luck! Thanks for all your continued help.