Database: products_gen_characteristics
Question: What are the product ids for products with two or more characteristics?
SQL: select t1.product_id from products as t1 join ref_colors as t2 on t1.color_code  =  t2.color_code join product_characteristics as t3 on t1.product_id  =  t3.product_id group by t1.product_id having count(*)  >=  2