Creates a test data set from star delta 0 - selecting ten sample coalesced urls and product names from the shelves for each vendor.

spinnaker.sql

SELECT product, url FROM 
  (SELECT ROW_NUMBER() OVER (PARTITION BY vendor ORDER BY product DESC) AS r, t.* FROM
    (SELECT vendor.name AS vendor, product.name AS product, COALESCE(shelf.detail_url, shelf.buy_url, NULL) AS url 
     FROM shelf
     JOIN product ON product.id = shelf.product_id
     JOIN vendor ON vendor.id = shelf.vendor_id) 
    AS t)
AS x
WHERE x.r <= 10