I’m not sure you really are counting as it doesn’t seem like your example will ever give you anything other than a 0 or a 1. It seems you just want to know if Mary has attended any courses in the Absence category or not.
Would a formula checking if there is an Absence category course work for you? A formula like:
IF(FIND('Absence', Category), 1, 0)
will check for the Absence category and give you either a 1 or a 0.
If I misunderstood and what you want to do is count all unique categories, then you can do a Rollover for the Categories table and use this in the aggregation formula:
and it will return a count of all unique categories.
Thanks for your answer, though I’m not sure I explained it correctly…
Mary attended AM2 course and AM3 course in Absence Category
John attended AM2 course in the Absence Category
James attended AM1 and AM2 in the Absence Category
Mark attended PL1 in the Procure to Pay Category
Need the count to return 3 unique attendees in the Absence Category and 1 in the Procure to Pay Category.
For now, I have separate VIEWS filtered by Category to return the correct number of unique attendees.
For the purpose (and life) of this project, that’s fine for now, though not ideal.