Assistance in writing Query / Query Logic.

Question

I have a peculiar requirement to fetch data.
Table Structure ( Sample ... although real table has more fields)
Order ( orderid varchar2(30), custid varchar2(30), status varchar2(1), createdon datetime )
Sample Data:
OrderID CustID AccID Status createdon
123 111 Y 20-Jan-2012 01:29:22
124 111 100 Y 22-Jan-2012 01:23:02
125 111 100 N 23-Jan-2012 02:34:24
126 111 100 N 28-Jan-2012 04:23:22
127 111 100 N 29-Jan-2012 07:32:26
123Cancel 111 100 N 31-Jan-2012 03:27:29
I want to write 2 Queries.
a. input is OrderId, Need to find out how many order's present with status = 'N' after that orderid provided.
b. input is OrderId, Need to find out what is the previous order with status = 'Y'
Note: There can be 100's of orders and Status would be Y on first come first serve basis... if one does not have status = 'Y' ie it is 'N' the following order's will never turn to final status = 'Y'.
There are millions of records in the table.
Your help for writing this query / logic would be highly appreciated. Am intending to do thru single query.
Best Regards
MH Doshi

Answer 1

select count(*) from order
where createdon >( select created from order where order_id = &order_id);
and status = 'N';
select * from (select a.*, rownum rn from (select order_id from order
where status = 'Y'
and createdon<(seelect createdon from order where order_id = &order_id)
order by createdon)) where rn=1