SELECT
  'web' AS channel,
  web.item,
  web.return_ratio,
  web.return_rank,
  web.currency_rank
FROM (
       SELECT
         item,
         return_ratio,
         currency_ratio,
         rank()
         OVER (
           ORDER BY return_ratio) AS return_rank,
         rank()
         OVER (
           ORDER BY currency_ratio) AS currency_rank
       FROM
         (SELECT
           ws.ws_item_sk AS item,
           (cast(sum(coalesce(wr.wr_return_quantity, 0)) AS DECIMAL(15, 4)) /
             cast(sum(coalesce(ws.ws_quantity, 0)) AS DECIMAL(15, 4))) AS return_ratio,
           (cast(sum(coalesce(wr.wr_return_amt, 0)) AS DECIMAL(15, 4)) /
             cast(sum(coalesce(ws.ws_net_paid, 0)) AS DECIMAL(15, 4))) AS currency_ratio
         FROM
           web_sales ws LEFT OUTER JOIN web_returns wr
             ON (ws.ws_order_number = wr.wr_order_number AND
             ws.ws_item_sk = wr.wr_item_sk)
           , date_dim
         WHERE
           wr.wr_return_amt > 10000
             AND ws.ws_net_profit > 1
             AND ws.ws_net_paid > 0
             AND ws.ws_quantity > 0
             AND ws_sold_date_sk = d_date_sk
             AND d_year = 2001
             AND d_moy = 12
         GROUP BY ws.ws_item_sk
         ) in_web
     ) web
WHERE (web.return_rank <= 10 OR web.currency_rank <= 10)
UNION
SELECT
  'catalog' AS channel,
  catalog.item,
  catalog.return_ratio,
  catalog.return_rank,
  catalog.currency_rank
FROM (
       SELECT
         item,
         return_ratio,
         currency_ratio,
         rank()
         OVER (
           ORDER BY return_ratio) AS return_rank,
         rank()
         OVER (
           ORDER BY currency_ratio) AS currency_rank
       FROM
         (SELECT
           cs.cs_item_sk AS item,
           (cast(sum(coalesce(cr.cr_return_quantity, 0)) AS DECIMAL(15, 4)) /
             cast(sum(coalesce(cs.cs_quantity, 0)) AS DECIMAL(15, 4))) AS return_ratio,
           (cast(sum(coalesce(cr.cr_return_amount, 0)) AS DECIMAL(15, 4)) /
             cast(sum(coalesce(cs.cs_net_paid, 0)) AS DECIMAL(15, 4))) AS currency_ratio
         FROM
           catalog_sales cs LEFT OUTER JOIN catalog_returns cr
             ON (cs.cs_order_number = cr.cr_order_number AND
             cs.cs_item_sk = cr.cr_item_sk)
           , date_dim
         WHERE
           cr.cr_return_amount > 10000
             AND cs.cs_net_profit > 1
             AND cs.cs_net_paid > 0
             AND cs.cs_quantity > 0
             AND cs_sold_date_sk = d_date_sk
             AND d_year = 2001
             AND d_moy = 12
         GROUP BY cs.cs_item_sk
         ) in_cat
     ) catalog
WHERE (catalog.return_rank <= 10 OR catalog.currency_rank <= 10)
UNION
SELECT
  'store' AS channel,
  store.item,
  store.return_ratio,
  store.return_rank,
  store.currency_rank
FROM (
       SELECT
         item,
         return_ratio,
         currency_ratio,
         rank()
         OVER (
           ORDER BY return_ratio) AS return_rank,
         rank()
         OVER (
           ORDER BY currency_ratio) AS currency_rank
       FROM
         (SELECT
           sts.ss_item_sk AS item,
           (cast(sum(coalesce(sr.sr_return_quantity, 0)) AS DECIMAL(15, 4)) /
             cast(sum(coalesce(sts.ss_quantity, 0)) AS DECIMAL(15, 4))) AS return_ratio,
           (cast(sum(coalesce(sr.sr_return_amt, 0)) AS DECIMAL(15, 4)) /
             cast(sum(coalesce(sts.ss_net_paid, 0)) AS DECIMAL(15, 4))) AS currency_ratio
         FROM
           store_sales sts LEFT OUTER JOIN store_returns sr
             ON (sts.ss_ticket_number = sr.sr_ticket_number AND sts.ss_item_sk = sr.sr_item_sk)
           , date_dim
         WHERE
           sr.sr_return_amt > 10000
             AND sts.ss_net_profit > 1
             AND sts.ss_net_paid > 0
             AND sts.ss_quantity > 0
             AND ss_sold_date_sk = d_date_sk
             AND d_year = 2001
             AND d_moy = 12
         GROUP BY sts.ss_item_sk
         ) in_store
     ) store
WHERE (store.return_rank <= 10 OR store.currency_rank <= 10)
ORDER BY 1, 4, 5
LIMIT 100