Drill-down using chart swapping or overlaying

Question

I am working on a pie chart which supports drill-downs. The
idea is that when a user clicks on a chart sector a column chart is
shown on top of the pie chart showing further distribution of
values in the selected sector.
My question is what is the right way to implement this kind
of pie chart supporting drill-downs?
Should I define both charts in MXML and then dynamically make
one invisible and the other one visible? How do I swap the charts?
Any sample code will be greatly appreciated.
Thanks.

Answer 1

I just re-read this and realize you want it on the same page. Same logic applies. Create a hidden item, a second chart region taking in the parameter from the first, and set it to show only when the hidden item is not null.
Let me know what you think:
http://htmldb.oracle.com/pls/otn/f?p=20332:1
Code for the first chart is:
select 'f?p='||:APP_ID||':1:::::P1_DRILLDOWN:'||cu.customer_id,
       cu.cust_first_name || ' ' || cu.cust_last_name,
       count(ord.order_id)
  from demo_orders ord,
       demo_customers cu
where cu.customer_id = ord.customer_id
group by 'f?p='||:APP_ID||':1:::::P1_DRILLDOWN:'||cu.customer_id,
cu.cust_first_name || ' ' || cu.cust_last_name2nd Chart:
select null,
       product_name,
       count(ite.product_id)
  from demo_orders ord,
       demo_order_items ite,
       demo_product_info pro
where ord.order_id = ite.order_id and
       ite.product_id = pro.product_id and
       ord.customer_id = :P1_DRILLDOWN
group by product_nameModify as necessary.