select I.store_nbr, max(petfood)
from(
select sum(S.item_quantity) as petfood
from((store_information as I join store_visits as V on I.store_nbr=V.store_nbr
join item_scan as S on S.visit_nbr=V.visit_nbr)
join item_desc as D on D.item_nbr=S.item_nbr)
)
where I.state='OH' and D.category_nbr='8'
group by I.store_nbr