Get only latest row, grouped by a column

Question

I have a large data-set of emails sent and status-codes.

ID Recipient           Date       Status
 1 someone@example.com 01/01/2010      1
 2 someone@example.com         


        

Answer 1

You can use the ranking functions for this. Something like (not tested):

WITH MyResults AS
(
   SELECT Recipient, Status, ROW_NUMBER() OVER( Recipient ORDER BY (  [date] DESC ) ) AS   [row_number]
   FROM Messages
)
SELECT MyResults.Recipient, MyCounts.EmailCount, MyResults.Status
FROM (
    SELECT Recipient, Count(*) EmailCount
    FROM Messages
    GROUP BY Recipient
) MyCounts
INNER JOIN MyResults
ON MyCounts.Recipient = MyResults.Recipient
WHERE MyResults.[row_number] = 1