How to get the first and the last record per group in SQL Server 2008?

Question

As the title suggests, I\'d like to select the first and last row of each set of rows grouped with a GROUP BY.

I\'ve this table with the following data

Answer 1

How about using ROW_NUMBER:

SQL Fiddle

WITH Cte AS(
    SELECT *,
        RnAsc = ROW_NUMBER() OVER(PARTITION BY [group] ORDER BY val),
        RnDesc = ROW_NUMBER() OVER(PARTITION BY [group] ORDER BY val DESC)
    FROM tbl
)
SELECT
    id, [group], val, start, [end]
FROM Cte
WHERE
    RnAsc = 1 OR RnDesc = 1
ORDER BY [group], val