SELECT * FROM
(
SELECT ROW_NUMBER() OVER (ORDER BY col_name ASC) AS rownumber, *
FROM
table_name
) AS foo
WHERE rownumber = n
Let me give you a real example. Assume that you have a table called "items" (it is not hard to imagine a table called "items", huh?) and you want to get the row which has the 5th greatest id just because you like it that way. I won't judge you for this request, I like the 3rd greatest better... Anyway, the query you will need is going to be something like this:
SELECT * FROM
(
SELECT ROW_NUMBER() OVER (ORDER BY id ASC) AS rownumber, *
FROM items
) AS foo
WHERE rownumber = 5
Hope it helps...