รายชื่อแพทย์ที่ไม่เคยนัดหมายใดๆ
List the name of physicians who never took any appointment.
df_physician = pd.DataFrame(columns = ['name', 'EmployeeID']); df_appointment = pd.DataFrame(columns = ['Physician'])
df_physician[~df_physician['EmployeeID'].isin(df_appointment['Physician'])]['name']