Duplicates /Multiple values over data range Oracle

I have a table where multiple users have update access.
Table Point_of_sale ( Brand, Sub_brand, value, start_date, end_date )

If user1 updates the value to $10 and user2 updates the value to $20 without putting end_date on the first record , it creates discrepancy.I need to find out all such values in the table.
Depending on when I’m running this query it should get results for all active records , meaning in below example if I’m running the query in JUN 2021 , the start_date is good for 2 records since it is > 1-JAN-2021 and 5-MAY-2021.

How can I make use of partition by /order by

Expected result of query

>Solution :

You appear to want to count the NULL values for each brand/sub-brand and then return the NULL values when there are more than two:

SELECT *
FROM   (
  SELECT p.*,
         COUNT(CASE WHEN end_date IS NULL THEN 1 END)
           OVER (PARTITION BY brand, sub_brand) AS num_null
  FROM   point_of_sale p
)
WHERE  num_null > 1
AND    end_date IS NULL;

Which, for the sample data:

create table Point_of_sale (Brand, Sub_Brand, Value, START_Date, End_Date) AS
SELECT 'Silverware', 'Spoon', 10, DATE '2020-01-01', DATE '2020-12-20' FROM DUAL UNION ALL
SELECT 'Silverware', 'Spoon', 20, DATE '2021-01-01', NULL FROM DUAL UNION ALL
SELECT 'Silverware', 'Spoon', 30, DATE '2021-05-05', NULL FROM DUAL;

Outputs:

If you want rows before today then use:

SELECT *
FROM   (
  SELECT p.*,
         COUNT(CASE WHEN end_date IS NULL THEN 1 END)
           OVER (PARTITION BY brand, sub_brand) AS num_null
  FROM   point_of_sale p
  WHERE  start_date <= SYSDATE
)
WHERE  num_null > 1
AND    end_date IS NULL;

fiddle