如何使用SQL处理类型2缓慢更改维度

Question

我有一个历史表，数据如下：

在我的情况下，product id（110,111,112）更改了price，因为我拥有与product_updateDate相同的产品，有时我可以使用相同的重复数据没有信息改变

+------+------------+--------------+---------------+-----------------------------+-------------------------+-------------------------+----------------+
| id   | product_id | product_name | product_Price |       product_addDate       |   product_UpdateDate    |      Insertdate_DB      | Updatedate_DB  |
+------+------------+--------------+---------------+-----------------------------+-------------------------+-------------------------+----------------+
|    1 |        110 |    DELL      |          1000 |    2017-03-01 08:00:00.000  | NULL                    | 2017-03-06 10:00:00.000 | NULL           |
|    2 |        111 |    HP        |           900 |    2017-03-01 08:00:00.000  | NULL                    | 2017-03-06 10:00:00.000 | NULL           |
| 3    |        112 |    Mac       |          1300 |    2017-03-01 08:00:00.000  | NULL                    | 2017-03-06 10:00:00.000 | NULL           |
| 4    |        113 |   Lenovo     |           950 |    2017-03-01 08:00:00.000  | NULL                    | 2017-03-06 10:00:00.000 | NULL           |
| 5    |        110 |   DELL       |           900 |    2017-03-04 08:00:00.000  | 2017-03-04 08:00:00.000 | 2017-03-07 10:00:00.000 | NULL           |
| 6    |        111 |    HP        |           800 |    2017-03-04 08:00:00.000  | 2017-03-04 08:00:00.000 | 2017-03-07 10:00:00.000 | NULL           |
| 7    |        112 |    Mac       |           120 |    2017-03-04 08:00:00.000  | 2017-03-04 08:00:00.000 | 2017-03-07 10:00:00.000 | NULL           |
+------+------------+--------------+---------------+-----------------------------+-------------------------+-------------------------+----------------+

我想要的是进行更新查询以获得结果：

 +----+------------+--------------+---------------+-------------------------+-------------------------+-------------------------+---------------+
| id | product_id | product_name | product_Price |     product_addDate     |   product_UpdateDate    |      Insertdate_DB      | Updatedate_DB |
+----+------------+--------------+---------------+-------------------------+-------------------------+-------------------------+---------------+
|  1 |        110 | DELL         |          1000 | 2017-03-01 08:00:00.000 | 2017-03-04 08:00:00.000 | 2017-03-06 10:00:00.000 | GETDATE()     |
|  2 |        111 | HP           |           900 | 2017-03-01 08:00:00.000 | 2017-03-04 08:00:00.000 | 2017-03-06 10:00:00.000 | GETDATE()     |
|  3 |        112 | Mac          |          1300 | 2017-03-01 08:00:00.000 | 2017-03-04 08:00:00.000 | 2017-03-06 10:00:00.000 | GETDATE()     |
|  4 |        113 | Lenovo       |           950 | 2017-03-01 08:00:00.000 | NULL                    | 2017-03-06 10:00:00.000 | NULL          |
|  5 |        110 | DELL         |           900 | 2017-03-04 08:00:00.000 | NULL                    | 2017-03-07 10:00:00.000 | NULL          |
|  6 |        111 | HP           |           800 | 2017-03-04 08:00:00.000 | NULL                    | 2017-03-07 10:00:00.000 | NULL          |
|  7 |        112 | Mac          |           120 | 2017-03-04 08:00:00.000 | NULL                    | 2017-03-07 10:00:00.000 | NULL          |
+----+------------+--------------+---------------+-------------------------+-------------------------+-------------------------+---------------+

以下查询可以更新product_UpdateDate

update tablename set product_UpdateDate=
case when tablename.product_UpdateDate is null then t.product_UpdateDate
else null end
from tablename 
join tablename t on tablename.product_id=t.product_id
and t.ID<>tablename.id `

但是，当我尝试更新此列时，我想更改Updatedate_DB GETDATE()值，所有行的值都为GETDATE()，但我只想更改行的{{1}}价值有变化

感谢您的帮助