แพทย์ John Dorian เป็นผู้สั่งจ่ายยาให้กับคนไข้จำนวนกี่ราย?
How many patients' prescriptions are made by physician John Dorian?
df_patient = pd.DataFrame(columns = ['SSN']); df_prescribes = pd.DataFrame(columns = ['patient', 'physician']); df_physician = pd.DataFrame(columns = ['employeeid', 'name'])
df_physician_id = df_physician[df_physician['name'] == 'John Dorian']['employeeid'].iloc[0]; df_patient[df_patient['SSN'].isin(df_prescribes[df_prescribes['physician'] == df_physician_id]['patient'])].count()[0]