Question: What are the product stock numbers with the attribute processed by most entries?
SQL: SELECT t1.product_stock_number FROM Catalog_Contents AS t1 JOIN Catalog_Contents_Additional_Attributes AS t2 ON t1.catalog_entry_id   =   t2.catalog_entry_id WHERE t2.attribute_value   =    ( SELECT attribute_value FROM Catalog_Contents_Additional_Attributes GROUP BY attribute_value ORDER BY count ( * )  DESC LIMIT 1 )