Now that I have a working SQL which groups by a field and also returns a related datetime field, I am trying to know if what I need to achieve is possible. Basically, the current SQL is as follow:

SELECT TOP 10 Event.RO_No,Min(Event.DateTime) AS LastUpdate
 FROM Event
 GROUP BY Event.RO_No
 ORDER BY MIN(Event.Datetime)

So, this returns something like this:

Ro_No       DateTime
  1         2007-12-17 14:41:25.704
  3         2007-12-17 14:42:25.704
  7         2007-12-17 14:43:25.704
 22         2007-12-18 15:41:25.704
 23         2007-12-19 16:41:25.704
 24         2008-12-20 07:41:25.704
 25         2009-12-17 08:41:25.704
 46         2009-12-17 05:41:25.704
 48         2009-12-18 05:41:25.704
 49         2009-12-19 14:41:25.704

From that SQL, I need to establish a relation into the RO table. This is accomplished by doing this:

SELECT RO.FirstName
FROM (SELECT TOP 10 Event.RO_No,Min(Event.DateTime) AS LastUpdate
 FROM Event
 GROUP BY Event.RO_No
 ORDER BY MIN(Event.Datetime)) Temp
INNER JOIN RO ON Temp.RO_No=RO.RO_No

So far so good, now the problem I am facing is that this log contains some old archive. So, not all RO_No are present in the RO table. Basically, the RO table is containing some recent records only. But, I need to start from the log. So, the goal here is trying to know if it is possible to make sure to collect the first 10 records which would also be records that exist in RO.