Combine Tables In Datasets

Dear All,

I have custom datasets to calculate total bandwidth from SSL VPN users, the data is from Log Type Traffic :

SELECT
srcip,
dstip,
user,
service,
sum(COALESCE(sentbyte, 0) + COALESCE(rcvdbyte, 0)) AS bandwidth,
sum(COALESCE(rcvdbyte, 0)) AS traffic_in,
sum(COALESCE(sentbyte, 0)) AS traffic_out
FROM
$log
WHERE
$filter
AND (logflag & 1 > 0)
AND(((lower(srcintf) = lower('ssl.TRUST_VDOM'))))
GROUP BY
srcip,
dstip,
user,
service
HAVING
sum(COALESCE(sentbyte, 0) + COALESCE(rcvdbyte, 0)) > 0
ORDER BY
bandwidth DESC

And now we require to know the duration of connection for each SSL VPN users, related with previous datasets. But I can't find any documentation yet. Is that possible to do?