my $perfdbh = DBI->connect("DBI:mysql:database=$database;host=$dbhost", "******", "******", {RaiseError => 1, AutoCommit => 1}) or die $DBI::errstr;

##</code><code>##

my $statement = "select $columns{$database} from $perftable where $query";
my ($days, $latest, $maxcpu, $avgcpu, $minfreemem, $avgfreemem) = ($perfdbh->selectrow_array($statement));

##</code><code>##

my ($days, $latest, $maxcpu, $avgcpu, $minfreemem, $avgfreemem) = ($perfdbh->selectrow_array("
select $columns{$database}
from $perftable
where $query"));

##</code><code>##

mysql> select ( count(*) / 288 ), max(date), max(usrpercent+nicepercent+syspercent+wiopercent), avg(usrpercent+nicepercent+syspercent+wiopercent), max(memused - memcache), avg(memused - memcache) from SERVER where epoch >= (select max(epoch)-3456000 from SERVER) and (time <= '09:00' or time >= '17:00');
+--------------------+-----------+---------------------------------------------------+---------------------------------------------------+-------------------------+-------------------------+
| ( count(*) / 288 ) | max(date) | max(usrpercent+nicepercent+syspercent+wiopercent) | avg(usrpercent+nicepercent+syspercent+wiopercent) | max(memused - memcache) | avg(memused - memcache) |
+--------------------+-----------+---------------------------------------------------+---------------------------------------------------+-------------------------+-------------------------+
|             0.0000 | NULL      |                                              NULL |                                              NULL |                    NULL |                    NULL | 
+--------------------+-----------+---------------------------------------------------+---------------------------------------------------+-------------------------+-------------------------+
1 row in set (0.01 sec)