Getting the N most recent rows over multiple grouping

Given this data

User_ID | Completion_Date |
—— | —— |
1 | 2016-07-20 |
1 | 2016-07-21 |
2 | 2016-07-20 |
2 | 2016-07-21 |
2 | 2016-07-22 |

;with CTE as
(SELECT *, 
        ROW_NUMBER() OVER (PARTITION BY User_ID 
                           ORDER BY Completion_Date DESC) Row_Num
FROM    Data)
SELECT * FORM CTE WHERE Row_Num <= n

Using n=1, you’ll get the one most recent row per user_id:

User_ID | Completion_Date |Row_Num |
—— | —— |—— |
1 | 2016-07-21 |1
2 | 2016-07-22 |1