I've been having the same issue described here. I'm having trouble recognising whether I have to set up a relationship between two tables that are linked by a lookup field. In my specific case, I have a StudentsT table with a [CountryID] field, and a CountriesT table with [ID] and [CountryName] fields. I already set-up a 1:M relationship between [ID] in CountriesT and [CountryID] in StudentsT (though I don't know if I'm suposed to do that).
Now comes the confusing part, and something that, despite its usefuleness, Gord Thompson's answer to the linked post didn't address, or I didn't understand (probably because it is such a basic thing). I'm not working with forms yet, so this is all at the table level. Do I set up the [CountryID] in StudentsT as a lookup to the [ID] in CountriesT? Or do I leave the relationship as is, and the only apply the lookup in the form itself?
I ask this because if I use the lookup at the table, the 1:M relationship I set up earlier seems extremely redundant (that's why I don't know whether it was ok to make that relationship, since the lookup already limits the input options to those stored in the table, ensuring integrity, right?).
Thanks for any clarification.