Knockhill มีกี่วัน?ไม่จำเป็นต้องใช้ตารางทั้งหมด
How many dates was knockhill?It is not neccessary to use all the tables.
 table_24547593_1:  (date [ VARCHAR ] circuit [ VARCHAR) ]
SELECT COUNT(date) FROM table_24547593_1 WHERE circuit = "Knockhill"