The query below joins two tables (networktraffic and domaintable) and sums up the total download traffic for each domain.. domainTable is just a lookup between domainId and the name of the domain...
SELECT domainTable.name, sum(NetworkTraffic.download) as "Weekly",(select sum(NetworkTraffic.download) from NetworkTraffic where date="2005-10-12") as "Daily"
LEFT JOIN domainTable ON domainTable.domainId = NetworkTraffic.domainId
WHERE date between "2005-10-10" AND "2005-10-16"
GROUP BY domainTable.name