SELECT *
FROM
  (SELECT i_category,
          i_class,
          i_brand,
          i_product_name,
          d_year,
          d_qoy,
          d_moy,
          s_store_id,
          sumsales,
          rank() OVER (PARTITION BY i_category
                       ORDER BY sumsales DESC) rk
   FROM
     (SELECT i_category,
             i_class,
             i_brand,
             i_product_name,
             d_year,
             d_qoy,
             d_moy,
             s_store_id,
             sum(coalesce(ss_sales_price*ss_quantity,0)) sumsales
      FROM store_sales,
           date_dim,
           store,
           item
      WHERE ss_sold_date_sk=d_date_sk
        AND ss_item_sk=i_item_sk
        AND ss_store_sk = s_store_sk
        AND d_month_seq BETWEEN 1200 AND 1200+11
      GROUP BY rollup(i_category, i_class, i_brand, i_product_name, d_year, d_qoy, d_moy,s_store_id))dw1) dw2
WHERE rk <= 100
ORDER BY i_category NULLS FIRST,
         i_class NULLS FIRST,
         i_brand NULLS FIRST,
         i_product_name NULLS FIRST,
         d_year NULLS FIRST,
         d_qoy NULLS FIRST,
         d_moy NULLS FIRST,
         s_store_id NULLS FIRST,
         sumsales NULLS FIRST,
         rk NULLS FIRST
LIMIT 100;