i understand what you're trying to do

what you need is a table which contains the valid combinations of year, type, and category

so if 10,20,80 is valid, and 10,20,10 is not valid, you need a table which has all the valid combinations in it, and then the inventory table can reference the composite key of this table, to ensure data integrity, i.e. to ensure that only the valid combinations can be entered into the inventory table

i was under the impression that your year/variety table was intended to satisfy this requirement