gistfile1.sql

WITH bob AS (
  WITH adena AS (
    SELECT
      prices.guid,prices.type,prices.store,prices.url,prices.datetime,prices.quantity,prices.price,prices.currency
    FROM prices
    INNER JOIN (
      SELECT
        guid,store,type,max(datetime) m
      FROM prices
      GROUP BY guid,store,type
    ) vew ON (prices.guid=vew.guid AND prices.store=vew.store AND prices.datetime=m AND prices.type=vew.type))
  SELECT DISTINCT ON (guid, type)
    *
  FROM adena
  ORDER BY guid, type, price ASC
)
SELECT
  price, guid, currency, datetime, stores.name AS store, quantity, type, urls.url AS url
FROM bob
JOIN urls ON (bob.url = urls.id)
JOIN stores ON (bob.store = stores.id)
ORDER BY price DESC;