How to delete duplicates in SQL table with Primary Key [duplicate] - sql-server

Question

This question already has answers here:
How can I remove duplicate rows?
(43 answers)
Closed 6 years ago.
As an example, consider the following table.
+-------+----------+----------+------------+
| ID(PK)| ClientID | ItemType | ItemID |
+-------+----------+----------+------------+
| 1 | 4 | B | 56 |
| 2 | 8 | B | 54 |
| 3 | 276 | B | 57 |
| 4 | 8653 | B | 25 |
| 5 | 3 | B | 55 |
| 6 | 4 | B | 56 |
| 7 | 4 | B | 56 |
| 8 | 276 | B | 57 |
| 9 | 8653 | B | 25 |
+-------+----------+----------+------------+
We have a process that's causing duplicates that we need to delete. In the example above, clients 4, 276, and 8653 should only ever have one ItemType/ItemID combination. How would I delete the extra rows that I don't need. So in this example, I'd need to delete all row contents of ID(PK)s 6, 7, 8, 9. Now this would need to happen on a much larger scale so I can't just go in one by one and delete the rows. Is there a query that will identify all ID(PK)s that aren't the lowest ID(PK) so I can delete them? I'm picturing a delete statement that operates on a subquery, but I'm open to suggestions. I've tried creating a rownumber to identify duplicates, however, because the table has a PK all rows are unique so that hasn't worked for me.
Thank you!
Edit: Here's the expected result
+-------+----------+----------+------------+
| ID(PK)| ClientID | ItemType | ItemID |
+-------+----------+----------+------------+
| 1 | 4 | B | 56 |
| 2 | 8 | B | 54 |
| 3 | 276 | B | 57 |
| 4 | 8653 | B | 25 |
| 5 | 3 | B | 55 |
+-------+----------+----------+------------+

Answer 1

You can use CTE:
;WITH ToDelete AS (
SELECT ROW_NUMBER() OVER (PARTITION BY ClientID, ItemType, ItemID
ORDER BY ID) AS rn
FROM mytable
)
DELETE FROM ToDelete
WHERE rn > 1