sel 202101 as calendar_year_month_id, base.source_system, 
count(distinct churn.source_Customer_id) churns, 
count(distinct base.source_Customer_id) base_count, 
churns*100.00/base_count||' %' as Churn_Rate
from 
(
    sel * from xyz.Customer_Base 
	where calendar_date between '2021-01-01' and '2021-01-31' and 
	Customer_Type_Group_Name <>'Mobile Prepaid' and source_system ='Voda'
) base  
left join 
(
    sel churn.* ,'SUN' as source_system_der
    from xyz.Customer_Churn churn 
    inner join product_grouping dpg
        on dpg.product_id=churn.bundle_id_pre and dpg.mark_group <> 'Mobile Prepaid' and churn.source_system= 'Voda'
        and actual_date between '2021-01-01' and '2021-02-01'
) churn 
    on extract(year from churn.actual_date) = extract(year from base.calendar_date)
    and extract(month from churn.actual_date) = extract(month from base.calendar_date)
    and trim(churn.source_Customer_id) = trim(base.source_Customer_id)
    and churn.source_system_der = base.source_system
where 1=1
group by 1,2