Oracle SQL - Displaying only net effect (unmatched) rows - sql

Question

Following is my sample table structure
Name Amount
A 100
A 100
A -100
A 100
A 100
A -100
B 10
A 100
There is no Primary Key in this table.
Desired Output:
Name Amount
A 100
A 100
B 10
A 100
Explanation:
I need to cancel out matching rows, i.e., one -100 nullifies one +100.
Therefore i need to display only rows that are not offset / not nullified one to one.
This can be done in PL/SQL by populating the rows to a temporary table and deleting one positive for every one corresponding negative. However, I require to do this on the fly using SQL statements.
Regards,
Raghu

Answer 1

You can enumerate the rows using row_number() and then use that to "cancel" them:
select t.name, t.amount
from (select t.*,
sum(amount) over (partition by name, abs(amount), seqnum) as sum_amount
from (select t.*,
row_number() over (partition by name, amount order by name) as seqnum
from t
) t
) t
where sum_amount <> 0;
Here is a db<>fiddle.

Answer 2

You can give each row a ROW_NUMBER unique to that name/amount pair and then count whether, for a name/ABS(amount) there are one or two values for each of those ROW_NUMBER and discard the rows where there are two (one positive and one negative):
SELECT name,
amount
FROM (
SELECT name,
amount,
COUNT( amount ) OVER ( PARTITION BY name, ABS( amount ), rn )
AS num_matches
FROM (
SELECT t.*,
ROW_NUMBER() OVER ( PARTITION BY name, amount ORDER BY ROWNUM ) AS rn
FROM table_name t
)
)
WHERE num_matches = 1
So, for your sample data:
CREATE TABLE table_name ( Name, Amount ) AS
SELECT 'A', +100 FROM DUAL UNION ALL
SELECT 'A', +100 FROM DUAL UNION ALL
SELECT 'A', -100 FROM DUAL UNION ALL
SELECT 'A', +100 FROM DUAL UNION ALL
SELECT 'A', +100 FROM DUAL UNION ALL
SELECT 'A', -100 FROM DUAL UNION ALL
SELECT 'B', +10 FROM DUAL UNION ALL
SELECT 'A', +100 FROM DUAL;
This outputs:
NAME | AMOUNT
:--- | -----:
A | 100
A | 100
A | 100
B | 10
db<>fiddle here

Answer 3

If there are never more negative values than positive it's a task for EXCEPT ALL. Oracle doesn't support it, but this is a rewrite:
select name, amount
from
(
select name, amount, row_number() over (partition by name, amount order by amount)
from tab
where amount > 0
minus
select name, -amount, row_number() over (partition by name, amount order by amount)
from tab
where amount < 0
) dt
or
with cte as
(
select name, amount, row_number() over (partition by name, amount order by amount) as rn
from tab
)
select name, amount
from
(
select name, amount, rn
from cte
where amount > 0
minus
select name, -amount, rn
from cte
where amount < 0
) dt