how many distinct names of the products have characteristc name warm?
SELECT count ( DISTINCT t1.product_name )  FROM products AS t1 JOIN product_characteristics AS t2 ON t1.product_id   =   t2.product_id JOIN CHARACTERISTICS AS t3 ON t2.characteristic_id   =   t3.characteristic_id WHERE t3.characteristic_name   =   "warm"
distinct names of the products refers to COUNT(DISTINCT product_name); characteristic name 'warm' refers to characteristic_name = 'warm';