Joining based on Sum of amount - oracle

Question

Basically there are 2 files
File 1 sample
Reference
Amount
AA1
1000
File 2 sample
Reference
Match_No
Side
Amount
AA1
123
Ledger
1000
BB1
123
Statement
500
CC1
123
Statement
500
Now the requirement is using the reference from File 1 extract the Match_No from file 2 where side = 'Ledger'
The script I think for this should be:-
select file2.match_no
from file1 join file2 on file1.reference = file2.reference
where side = 'Ledger'
Now after extracting Match_No where side = Ledger, for the same Match_No extract all the references from file 2 where side ='Statement' and sum of file2.amounts (where side='Statement') = file2.amount(where side = Ledger)

Answer 1

This is how I understood what you are saying. See if it helps.
SQL> with
2 -- Sample data; you have it already & don't type it
3 file_1 (reference, amount) as
4 (select 'aa1', 1000 from dual),
5 file_2 (reference, match_no, side, amount) as
6 (select 'aa1', 123, 'Ledger' , 1000 from dual union all
7 select 'bb1', 123, 'Statement', 500 from dual union all
8 select 'cc1', 123, 'Statement', 500 from dual
9 ),
10 -- Useful code begins here.
11 -- Query you posted (I added "B.AMOUNT" and used it in line #21)
12 qyp as
13 (select b.match_no, b.amount
14 from file_1 a join file_2 b on a.reference = b.reference
15 where b.side = 'Ledger'
16 )
17 -- The final query
18 select b.reference
19 from file_2 b join qyp q on q.match_no = b.match_no
20 where b.side = 'Statement'
21 and q.amount = (select sum(c.amount)
22 from file_2 c
23 where c.match_no = b.match_no
24 and c.side = 'Statement'
25 );
REF
---
cc1
bb1
SQL>