นับจำนวนผู้สมัคร ไม่จำเป็นต้องใช้ตารางทั้งหมด
Count the number of candidates.It is not neccessary to use all the tables.
 candidate:  candidate_id [ number]  people_id [ number]  poll_source [ text]  date [ text]  support_rate [ number]  consider_rate [ number]  oppose_rate [ number]  unsure_rate [ number] 
SELECT COUNT(*) FROM candidate