Question

Table
P_ID   I_ID   S_ID  T_ID Column  Column1



 -- (<Column1> supposed to be <Column>.<Table>-<Column>.<Table1>)


Table

P_ID   I_ID   S_ID  T_ID Column

I ran this query on source table:

select <column> from 
<TABLE>
where 
i_id='<value>';

and i get the output as 9000
then i run this query on target to test id Column1 is getting correct values

select P_ID, I_ID, S_ID, T_ID, 
sum(<column>)
from 
<TABLE> F,<TABLE2> PO
where 
F.P_ID = PO.P_ID
and F.I_ID=PO.I_ID
and F.FLAG='Y'  --something that we need
and T_id>='2012001'  --just for results for 2012
and F.I_id='<Value>'
group by F.P_ID, F.I_ID, F.S_ID, F.T_ID
order by 1;



Here i get Output as
  P_ID     I_ID           S_ID          T_ID           sum(<column>)
 <Value>  <Value>         <Value>      <Value>              18000    

Answer 1

Obviously there are multiple rows in PO for each row in F.

Also, change your query to the more modern (since 1996!) join syntax:

from <TABLE> F
join <TABLE2> PO ON F.P_ID = PO.P_ID and F.I_ID=PO.I_ID
where F.FLAG='Y'
...

Edited:

If you just want to assert that there is a row in PO (not caring about how many rows) use exists():

select P_ID, I_ID, S_ID, T_ID, 
sum(<column>)
from <TABLE> F
where exists (
    select * from <TABLE2> PO 
    where F.P_ID = PO.P_ID
    and F.I_ID=PO.I_ID)
and F.FLAG='Y'  --something that we need
and T_id>='2012001'  --just for results for 2012
and F.I_id='<Value>'
group by F.P_ID, F.I_ID, F.S_ID, F.T_ID
order by 1;