Selects 10 product/name pairs for each vendor across all vendors.

spinnaker

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

Also, wish I could do a push request!