WITH inv AS
  (SELECT w_warehouse_name,
          w_warehouse_sk,
          i_item_sk,
          d_moy,
          stdev,
          mean,
          CASE mean
              WHEN 0 THEN NULL
              ELSE stdev/mean
          END cov
   FROM
     (SELECT w_warehouse_name,
             w_warehouse_sk,
             i_item_sk,
             d_moy,
             stddev_samp(inv_quantity_on_hand)*1.000 stdev,
             avg(inv_quantity_on_hand) mean
      FROM inventory,
           item,
           warehouse,
           date_dim
      WHERE inv_item_sk = i_item_sk
        AND inv_warehouse_sk = w_warehouse_sk
        AND inv_date_sk = d_date_sk
        AND d_year =2001
      GROUP BY w_warehouse_name,
               w_warehouse_sk,
               i_item_sk,
               d_moy) foo
   WHERE CASE mean
             WHEN 0 THEN 0
             ELSE stdev/mean
         END > 1)
SELECT inv1.w_warehouse_sk wsk1,
       inv1.i_item_sk isk1,
       inv1.d_moy dmoy1,
       inv1.mean mean1,
       inv1.cov cov1,
       inv2.w_warehouse_sk,
       inv2.i_item_sk,
       inv2.d_moy,
       inv2.mean,
       inv2.cov
FROM inv inv1,
     inv inv2
WHERE inv1.i_item_sk = inv2.i_item_sk
  AND inv1.w_warehouse_sk = inv2.w_warehouse_sk
  AND inv1.d_moy=1
  AND inv2.d_moy=1+1
ORDER BY inv1.w_warehouse_sk NULLS FIRST,
         inv1.i_item_sk NULLS FIRST,
         inv1.d_moy NULLS FIRST,
         inv1.mean NULLS FIRST,
         inv1.cov NULLS FIRST,
         inv2.d_moy NULLS FIRST,
         inv2.mean NULLS FIRST,
         inv2.cov NULLS FIRST;