How do i write this in sql ? (another headcracker challenging report)

Question

hi guys!,
I need to create / generate a report. I intend to do all this with pure SQL alone.
Been cracking my head for days but to no avail.
Hope you gurus here will straightened me out.
Here it goes. i Have a table
TABLE USAGE_REPORT
Date DATE -- everyday's date
BalanceCF NUMBER -- an initial start amount or ( balancebf)
Topup_amount NUMBER -- amount of topup that day
Usage1 NUMBER -- amount of $ use on certain prod
Usage2 NUMBER -- amount of $ use on certain prod
BalanceBF NUMBER -- BalanceCF + topup - usage1 -usage2 (which is also the next date BalanceCF)
Example1
please see this link
http://img9.imageshack.us/img9/708/88149028.gif
asumming my sql is
WITH dates AS
SELECT TRUNC(SYSDATE) + level dmy
FROM DUAL CONNECT BY level < 366
TopUP as
SELECT trunc(purchase_date) dated, sum(payment_amount)
FROM purchase
GROUP by trunc(purchase_date)
Usage1 as
SELECT trunc(connect_date) dated, sum(charged_amount)
FROM tab1
WHERE prod_id = 'xxx'
GROUP BY trunc(connect_date)
Usage2 as
SELECT trunc(connect_date) dated, sum(charged_amount)
FROM tab2
WHERE prod_id = 'yyy'
GROUP BY trunc(connect_date)
SELECT * FROM DATES D
LEFT OUTER JOIN TOPUP T
ON (D.DMY = T.DATED)
LEFT OUTER JOIN USAGE1 U1
ON (D.DMY = U1.DATED)
LEFT OUTER JOIN USAGE2 U2
ON (D.DMY = U2.DATED);
however
q1) how do i start 'initiate' the 1st row
BALANCECF so that i can do the calculation
of
BALANCECF + TOPUP - USAGE1 - USAGE2 = BALANCEBF
q2) how do i bring the value of BALANCEBF into the 2nd row of BALANCECF to do further calculation ?
q3) is it has something to do with connect by ? parent-child relationship
q4) in short how do i make it look like the attach pic above?
Please help!
Best Regards,
Noob

Answer 1

I am using 200 as initial balance_cf. You did not provide sample data, so code below is not tested:
WITH dates as (
               SELECT  TRUNC(SYSDATE) + level dmy,
                       200 balance_cf
                 FROM  DUAL
                 CONNECT BY level < 366
     topUP as (
               SELECT  trunc(purchase_date) dated,
                       sum(payment_amount) topup_amount
                 FROM  purchase
                 GROUP by trunc(purchase_date)
    Usage1 as (
               SELECT  trunc(connect_date) dated,
                       sum(charged_amount) usage_amount
                 FROM  tab1
                 WHERE prod_id = 'xxx'
                 GROUP BY trunc(connect_date)
    Usage2 as (
               SELECT  trunc(connect_date) dated,
                       sum(charged_amount) usage2_amount
                 FROM  tab2
                 WHERE prod_id = 'yyy'
                 GROUP BY trunc(connect_date)
SELECT  dmy,
        balance_cf + sum(topup_amount - usage1_amount - usage2_amount) over order by dmy rows between unbounded preceding and 1 preceding) balance_cf
        topup_amount,
        usage1_amount,
        usage2_amount,
        balance_cf + sum(topup_amount - usage1_amount - usage2_amount) over order by dmy) balance_bf
  FROM  DATES D LEFT OUTER JOIN TOPUP T ON (D.DMY = T.DATED)
                LEFT OUTER JOIN USAGE1 U1 ON (D.DMY = U1.DATED)
                LEFT OUTER JOIN USAGE2 U2 ON (D.DMY = U2.DATED)
  ORDER BY dmy
/SY.