Question

I struggling with a problem I have in TSQL, I need to get the top 10 results for each user from a table that might contain more than 10 results.

My natural (and procedurally minded) approach is “for each user in table T select the top 10 results ordered by date”.

Each time I try to formulate the question in my mind in a set based approach, I keep running into the term “foreach”.

Is it possible to do something like this:

SELECT *
FROM table AS t1
INNER JOIN (
    SELECT TOP 10 *
    FROM table AS t2
    WHERE t2.id = t1.id
    ORDER BY date DESC
)

Or even

SELECT (    SELECT TOP 10 *
             FROM table AS t2
             WHERE t2.id = t1.id
             ORDER BY date    )
FROM table AS t1

Or is there another solution to this using temp tables that I should think about?

EDIT:

Just to be perfectly clear – I need to the top 10 results for each user in the table, e.g. 10 * N where N = number of users.

EDIT:

In response to a suggestion made by RBarryYoung, I’m having an issue, which is best demonstrated with code:

CREATE TABLE #temp (id INT, date DATETIME)

INSERT INTO #temp (id, date) VALUES (1, GETDATE())
INSERT INTO #temp (id, date) VALUES (1, GETDATE())

SELECT *
FROM #temp AS t1
CROSS APPLY (
 SELECT TOP 1 *
 FROM #temp AS t2
 WHERE t2.id = t1.id
 ORDER BY t2.date DESC
) AS t2

DROP TABLE #temp

Running this, you can see that this doesn’t limit the results to the TOP 1… Am I doing something wrong here?

EDIT:

It seems my last example provided a bit of confusion. Here is an example showing what I want to do:

CREATE TABLE #temp (id INT, date DATETIME)
INSERT INTO #temp (id, date) VALUES (1, GETDATE())
INSERT INTO #temp (id, date) VALUES (1, GETDATE())
INSERT INTO #temp (id, date) VALUES (1, GETDATE())
INSERT INTO #temp (id, date) VALUES (2, GETDATE())

SELECT *
FROM #temp AS t1
CROSS APPLY
(
    SELECT TOP 2 *
 FROM #temp AS t2
    WHERE t2.id = t1.id
    ORDER BY t2.date DESC
) AS t2

DROP TABLE #temp

This outputs:

1 2009-08-26 09:05:56.570 1 2009-08-26 09:05:56.583
1 2009-08-26 09:05:56.570 1 2009-08-26 09:05:56.583
1 2009-08-26 09:05:56.583 1 2009-08-26 09:05:56.583
1 2009-08-26 09:05:56.583 1 2009-08-26 09:05:56.583
1 2009-08-26 09:05:56.583 1 2009-08-26 09:05:56.583
1 2009-08-26 09:05:56.583 1 2009-08-26 09:05:56.583
2 2009-08-26 09:05:56.583 2 2009-08-26 09:05:56.583

If I use distinct:

SELECT DISTINCT t1.id
FROM #temp AS t1
CROSS APPLY
(
    SELECT TOP 2 *
 FROM #temp AS t2
    WHERE t2.id = t1.id
    ORDER BY t2.date DESC
) AS t2

I get

1
2

I need

1
1
2

Does anyone know if this is possible?

EDIT:

The following code will do this

WITH RowTable AS
(
SELECT 
 id, date, ROW_NUMBER() OVER (PARTITION BY id ORDER BY date DESC) AS RowNum
FROM #temp 
)
SELECT *
FROM RowTable
WHERE RowNum <= 2;

I posted in the comments, but there is no code formatting, so it doesn’t look very nice.

Answer 1

select userid, foo, row_number() over (partition by userid order by foo)  as rownum from table where rownum <= 10