How can we set Fetch request to fetch single attribute? and also how to apply join query to retrieve data from core data?

Question

hi, I am using core data which has two tables. I want to fetch attribute "VID" from table "DOSE" and based on this result i want to fetch the corresponding name of vaccine from another table "Vaccine".how can i set Fetch request to retrive just one attribute? And is there any mechanism to join the query through which based on the retrived VID i get VaccineName from other table?