Column is invalid in the select list because it is not contained in either an aggregate function or the GROUP BY clause.

Question

Clearly, when GROUP BY clause used, columns that are not aggregate function should be part of the group by clause. The problem here is, I cannot contain HTTPADDRESS & DATEENTERED columns in GROUP BY clause. Also, I dont know a function that will give me the latest entries of all.

edit: I use sql-server. I would use LAST function if I were using access.

SQL = "SELECT VISITORIP, HTTPADDRESS, DATEENTERED"
SQL = SQL & " FROM STATS"
SQL = SQL & " WHERE DATEENTERED BETWEEN '" & OnlineTime & "' AND '" & NOW() & "'"
SQL = SQL & " GROUP BY VISITORIP"
SQL = SQL & " ORDER BY DATEENTERED DESC"
Set objOnVisitors = objConn.Execute(SQL)

Answer 1

You have to self-join back:

WITH LASTVISIT AS (
    SELECT VISITORIP, MAX(DATEENTERED) AS DATEENTERED
    FROM STATS
    WHERE DATEENTERED BETWEEN @STARTTIME AND @ENDTIME
    GROUP BY VISITORIP
)
SELECT STATS.VISITORIP, STATS.HTTPADDRESS, STATS.DATEENTERED
FROM STATS
INNER JOIN LASTVISIT
    ON LASTVISIT.VISITORIP = STATS.VISITORIP
    AND LASTVISIT.DATEENTERED = STATS.DATEENTERED
ORDER BY STATS.DATEENTERED DESC

Note, this assumes a given VISITORIP will have a unique maximum DATEENTERED in the range.