SQL creates high server load?
For some reason, my host yelled at me because one of my SQL queries was creating too much server load. Is the SQL string inefficient and is something causing it to go longer then it should? I have never ran into a problem with it, but I'm guessing now that there are more rows in my "offer" table it may create more stress.
$sql = "SELECT offers.category, COUNT(DISTINCT SS.offerid) as howmany "
. " FROM offers LEFT JOIN ( "
. " SELECT category AS cat, offerid FROM offers "
. " WHERE countries LIKE '%$country%' "
. " AND offerid NOT IN (SELECT offerid FROM completed_offers WHERE username='$usr') "
. " ) AS SS "
. " ON offers.category = SS.cat "
. " GROUP BY offers.category ORDER BY offers.category";