บอกจำนวนรุ่นน้องในทีมมาครับ ไม่จำเป็นต้องใช้ทุกโต๊ะ
tell me the number of juniors on the team .It is not neccessary to use all the tables.
 table_204_534:  id [ number]  "#" [ number]  "name" [ text]  "height" [ text]  "position" [ text]  "class" [ text]  "hometown" [ text] 
SELECT COUNT(*) FROM table_204_534 WHERE "class" = 'jr'