มีกี่มณฑลที่มีเหรียญเงินอย่างน้อยหนึ่งเหรียญ ?ไม่จำเป็นต้องใช้โต๊ะทั้งหมด
how many counties have at least one silver medal ?It is not neccessary to use all the tables.
 table_203_70:  id [ number]  "rank" [ number]  "nation" [ text]  "gold" [ number]  "silver" [ number]  "bronze" [ number]  "total" [ number] 
SELECT COUNT("rank") FROM table_203_70 WHERE "silver" >= 1