SQL Server: CTE, how to get last row number

I have a CTE like this:

;WITH Lastdt AS
(
    SELECT database_name, backup_finish_date,
    ROW_NUMBER() OVER (PARTITION BY database_name ORDER BY backup_finish_date, database_name) AS 'RowNumber'
    FROM bckHist
) 
SELECT database_name, backup_finish_date
FROM Lastdt
WHERE RowNumber = '7'

How can I get last row with highest number from the query (replace hardcoded 7)?

Answer

If you really need only last row (from your query) then it even simpler (for given case):

select database_name, max(backup_finish_date)
from bckHist
group by database_name