Mgmaplus

#Merge dataframes
all_sales_data = sales_date_customer.merge(employees_data, on = 'EmployeeName', how = 'left')
#New column CommissionEarned
all_sales_data['SalesCommission'] = all_sales_data['TotalDue'] * all_sales_data['CommissionPct']

#Grouping results by employee and year
commission_per_employee_per_year = all_sales_data.groupby(['OrderYear','EmployeeName']).sum()

#Sort and select with loc year 2012 results
commission_per_employee_per_year.sort_values(by='SalesCommission', ascending = True, inplace = True)