select top N records for each entity - sql

Question

I have a table like below -
ID | Reported Date | Device_ID
-------------------------------------------
1 | 2016-03-09 09:08:32.827 | 1
2 | 2016-03-08 09:08:32.827 | 1
3 | 2016-03-08 09:08:32.827 | 1
4 | 2016-03-10 09:08:32.827 | 2
5 | 2016-03-05 09:08:32.827 | 2
Now, i want a top 1 row based on date column for each device_ID
Expected Output
ID | Reported Date | Device_ID
-------------------------------------------
1 | 2016-03-09 09:08:32.827 | 1
4 | 2016-03-10 09:08:32.827 | 2
I am using SQL Server 2008 R2. i can go and write Stored Procedure to handle it but wanted do it with simple query.
****************EDIT**************************
Answer by 'Felix Pamittan' worked well but for 'N' just change it to
SELECT
Id, [Reported Date], Device_ID
FROM (
SELECT *,
Rn = ROW_NUMBER() OVER(PARTITION BY Device_ID ORDER BY [ReportedDate] DESC)
FROM tbl
)t
WHERE Rn >= N
He had mentioned this in comment thought to add it to questions so that no body miss it.

Answer 1

Use ROW_NUMBER:
SELECT
Id, [Reported Date], Device_ID
FROM (
SELECT *,
Rn = ROW_NUMBER() OVER(PARTITION BY Device_ID ORDER BY [ReportedDate] DESC)
FROM tbl
)t
WHERE Rn = 1

Answer 2

You can also try using CTE
With DeviceCTE AS
(SELECT *, ROW_NUMBER() OVER(PARTITION BY Device_ID ORDER BY [Reported Date] DESC) AS Num
FROM tblname)
SELECT Id, [Reported Date], Device_ID
From DeviceCTE
Where Num = 1

Answer 3

If you can't use an analytic function, e.g. because your application layer won't allow it, then you can try the following solution which uses a subquery to arrive at the answer:
SELECT t1.ID, t2.maxDate, t1.Device_ID
INNER JOIN
(
SELECT Device_ID, MAX([Reported Date]) AS maxDate
FROM yourTable
GROUP BY Device_ID
) t2
ON t1.Device_ID = t2.Device_ID AND t1.[Reported Date] = t2.maxDate

Answer 4

Select * from DEVICE_TABLE D
where [Reported Date] = (Select Max([Reported Date]) from DEVICE_TABLE where Device_ID = D.Device_ID)
should do the trick, assume that "top 1 row based on date column" means that you want to select the latest reported date of each Device_ID ?
As for your title, select top 5 rows of each Device_ID
Select * from DEVICE_TABLE D
where [Reported Date] in (Select top 5 [Reported Date] from DEVICE_TABLE D where Device_ID = D.Device_ID)
order by Device_ID, [Reported Date] desc
will give you the top 5 latest reports of each device id.
You may want to sort out the top 5 date if your data isn't in order...

Answer 5

Again with no analytic functions you can use CROSS APPLY :
DECLARE #tbl TABLE(Id INT,[Reported Date] DateTime , Device_ID INT)
INSERT INTO #tbl
VALUES
(1,'2016-03-09 09:08:32.827',1),
(2,'2016-03-08 09:08:32.827',1),
(3,'2016-03-08 09:08:32.827',1),
(4,'2016-03-10 09:08:32.827',2),
(5,'2016-03-05 09:08:32.827',2)
SELECT r.*
FROM ( SELECT DISTINCT Device_ID FROM #tbl ) d
CROSS APPLY ( SELECT TOP 1 *
FROM #tbl t
WHERE d.Device_ID = t.Device_ID ) r
Can be easily modified to support N records.
Credits go to wBob answering this question here