我有一个查询（sql server 2017），在同一天找到两个不同的折扣。

WITH CTE AS (SELECT    [date_id], [good_id], [store_id], [name_promo_mech], [discount],
                       RN = DENSE_RANK() OVER (PARTITION BY [date_id], [good_id], [store_id], [name_promo_mech]
                       ORDER BY [discount]) + 
                       DENSE_RANK() OVER (PARTITION BY [date_id], [good_id], [store_id], [name_promo_mech]
                       ORDER BY [discount] DESC) - 1

                       FROM [dbo].[ds_promo_list_by_day_new] AS PL
                       )

SELECT * FROM CTE 
WHERE RN > 1;
GO

查询结果：

+------------+----------+---------+-----------------+----------+----+
| date_id    | store_id | good_id | name_promo_mech | discount | RN |
+------------+----------+---------+-----------------+----------+----+
| 2017-01-01 | 3        | 98398   | January 2017    | 15       | 2  |
+------------+----------+---------+-----------------+----------+----+
| 2017-01-01 | 3        | 98398   | January 2017    | 40       | 2  |
+------------+----------+---------+-----------------+----------+----+
| 2017-01-01 | 5        | 98398   | January 2017    | 15       | 3  |
+------------+----------+---------+-----------------+----------+----+
| 2017-01-01 | 5        | 98398   | January 2017    | 40       | 3  |
+------------+----------+---------+-----------------+----------+----+
| 2017-01-01 | 5        | 98398   | January 2017    | 30       | 3  |
+------------+----------+---------+-----------------+----------+----+

现在我想对source表中所有唯一的good\u id、store\u id、name\u promo\u merch进行相同的折扣。这是有规律的。例如，对于good\u id=98398，store\u id=3，name\u promo\u mech=n'january 2017'行，有10个条目有15折，20个条目有40折，那么15折应该替换为40折。但是，如果每个折扣的条目数相同，则为所有条目设置最大折扣。
我能做这个吗？源表中的行数约为1亿。