select i_product_name
     , i_brand
     , i_class
     , i_category
     , avg(inv_quantity_on_hand) qoh
from inventory
   , date_dim
   , item
where inv_date_sk = d_date_sk
  and inv_item_sk = i_item_sk
  and d_month_seq between 1200 and 1200 + 11
group by rollup (i_product_name
       , i_brand
       , i_class
       , i_category)
order by qoh, i_product_name, i_brand, i_class, i_category limit 100