ประเทศใดมีเหรียญเงินมากเท่ากับเม็กซิโกและตุรกีรวมกัน ?ไม่จำเป็นต้องใช้โต๊ะทั้งหมดเลย
which nation had as many silver medals as mexico and turkey combined ?It is not neccessary to use all the tables.
 table_204_311:  id [ number]  "rank" [ number]  "nation" [ text]  "gold" [ number]  "silver" [ number]  "bronze" [ number]  "total" [ number] 
SELECT "nation" FROM table_204_311 WHERE "silver" = (SELECT SUM("silver") FROM table_204_311 WHERE "nation" IN ('mexico', 'turkey'))