Question

This query gets the desired rows -grouped by subject- and I also want to know the items count in each group.

SELECT log.* FROM [hm_deliverylog] AS log
WHERE log.deliveryid IN
    (
        SELECT MAX([deliveryid])  FROM [hm_deliverylog]
        WHERE [deliverytime] > DATEADD(HOUR, -12, GETDATE())
        GROUP BY deliverysubject
    )

ORDER BY deliveryid DESC

How can I count the groups? Like below?

SELECT joined.groupcount, log.* FROM [hm_deliverylog] AS log

P.S: Imagine the Gmail inbox; it displays the newest message and shows the message count. I want to group the messages with same subject and count them…

Answer 1

One way is to put the COUNT() calculation in the subquery and instead of using IN, make that a derived table to be joined:

SELECT log.* 
     , grp.cnt AS groupcount
FROM 
    [hm_deliverylog] AS log
  JOIN 
    (
        SELECT MAX([deliveryid]) AS deliveryid
             , COUNT(*) AS cnt  
        FROM [hm_deliverylog]
        WHERE [deliverytime] > DATEADD(HOUR, -12, GETDATE())
        GROUP BY deliverysubject
    ) AS grp
    ON grp.deliveryid = log.deliveryid
ORDER BY 
    log.deliveryid DESC ;