Need help with Performance Tuning

Question

Following query takes 8 secs. Any help will be appreciated
SELECT SUM(FuturesMarketVal) FuturesMarketVal
FROM (SELECT CASE WHEN null IS NULL THEN FuturesMarketVal
ELSE DECODE(FUTURES_NAME, null, FuturesMarketVal, 0)
END FuturesMarketVal
FROM (SELECT SUM( (a.FUTURES_ALLOC * (NVL(b.Futures_EOD_Price,0)/100 - NVL(c.Futures_EOD_Price,0)/100) * a.CONTRACT_SIZE) / DECODE(a.CONTRACT_SIZE,100000,1,1000000,4,3000000,12,1) ) FuturesMarketVal,
a.FUTURES_NAME
FROM cms_futures_trans a,
cms_futures_price b,
cms_futures_price c
          Where c.history_date (+) = TO_DATE(fas_pas_pkg.get_weekday(to_date('12/30/2005') - 1),'mm/dd/yyyy')
          and a.FUTURES_NAME = b.FUTURES_NAME (+)
AND a.trade_date < TO_DATE('12/30/2005','mm/dd/yyyy')
AND b.history_date (+) = TO_DATE('12/30/2005','mm/dd/yyyy')
AND a.FUTURES_NAME = c.FUTURES_NAME (+)
GROUP BY a.FUTURES_NAME
/

Answer 1

Eric:
But there are only 5 records in cms_futures_price and 10 in cms_futures_trans :-)
OP:
I'm not usre what you are trying to fo here, but a couple of comments.
Since NULL IS NULL will always be true, you don;t really need the CASE statement. as it stands, your query will always return FuturesMarketVal. If the results are correct, then you can do without the DECODE as well.
Why are you calling fas_pas_pkg.get_weekday with a constant value? Can you not just use whatever it returns as a constant instead of calling the function?
Are you sure you need all those outer joins? They almost guarantee full scans of the outer joined tables.
Perhaps if you post some representative data from the two tables and an explanation of what you are trying to accomplish someone may have a better idea.
John