ชิงแชมป์โลกจำนวนเท่าใด ?ไม่จำเป็นต้องใช้ทุกโต๊ะ
what is the number of world championships ?It is not neccessary to use all the tables.
 table_203_715:  id [ number]  "year" [ number]  "competition" [ text]  "venue" [ text]  "position" [ text]  "notes" [ text] 
SELECT COUNT(*) FROM table_203_715 WHERE "competition" = 'world championships'