มีการนัดหมายทั้งหมดกี่โต๊ะไม่จำเป็นต้องใช้ทุกโต๊ะ
How many appointments are there?It is not neccessary to use all the tables.
 appointment:  appointmentid [ number]  patient [ number]  prepnurse [ number]  physician [ number]  start [ time]  end [ time]  examinationroom [ text] 
SELECT COUNT(*) FROM appointment