Try

SELECT Temp.NoThread, (SELECT COUNT(*) FROM Thread WHERE NoThread = Temp.NoThread)
FROM 
(SELECT Top 10 NoThread FROM Thread ORDER BY Numero DESC) Temp

>I would like to retrieve the count from a derived SQL. I am not sure about the best approach to use. This is the SQL I have:
>
>

>SELECT Temp.NoThread
>FROM 
>(SELECT Top 10 NoThread FROM Thread ORDER BY Numero DESC) Temp
>

>
>So, in the result, I get all the keys that I need for the most recent 10 threads. However, based on those keys, I would now like to include a column for the count. Thread.NoThread have several occurences in the table. So, the result would include a column for the count having a value from 1 to x.