Want to avoid cartesian Product but cannot avoid it some how.

Question

Hi,
I am using oracle 10G .
trying to draft a query which is resulting in absurd results.
select i.corr_acc_no, sum(amtsign.amount_6) from item i,
(select corr_Acc_no,flag_2,decode(fund_code,'C',amount_6,amount_6*-1) amount_6 from item
where corr_AcC_no in (select corr_acc_no from bank where local_Acc_no in ('MBL-SEG-NZD'))and flag_2=0) AmtSign
where i.corr_acc_no=amtsign.corr_acc_no
and i.flag_2=0
group by  i.corr_acc_no
Basically the inner query, which i am using as the second table in the join, gives 13 results. I want to sum the amount_6 field in main select clause which I want to get from results of
(select corr_Acc_no,flag_2,decode(fund_code,'C',amount_6,amount_6*-1) amount_6 from item
where corr_AcC_no in (select corr_acc_no from bank where local_Acc_no in ('MBL-SEG-NZD'))and flag_2=0)
The sum took too much time so i drafted simple query to check how many rows are returned by removing sum and i noticed it gives a Cartesian product with 169 rows instead of just 13. I have 2 join conditions but the value for corr_Acc_no is same for all 13 rows, i can't use amount_6 as join becuase i am changing it's sign  in the inner query. Please advise.

Answer 1

Thanks to both of you. @LakmalRajapakse your answer is bang on right. I did the same way after I posted this. I realized there's no point joining item with itself when I can get it done in single query. It's just that I was having hard time with 'Case' in select to get whatever I want,so I tried this logic. But then gave a try to decode, it worked. Thanks anyways.