Faster alternative 1:

my %hash;
my %rec;
my $sth = $db->prepare ("select * from tablename");
$sth->execute;
$sth->bind_columns (\@hash{@{$sth->{NAME_lc}}});
while ($sth->fetch) {
    $hash{$rec{week}} = [ $rec{month}, $rec{workperiod} ];
    }
[download]

Faster alternative 2:

my %hash;
my $sth = $db->prepare ("select week, month, workperiod from tablename
+");
$sth->execute;
$sth->bind_columns (\my ($week, $month, $workperiod));
while ($sth->fetch) {
    $hash{$week} = [ $month, $workperiod ];
    }
[download]

Readabler alternative 3:

my $dbh = DBI->connect ("dbi:$driver:", "user", "pass", { FetchHashKey
+Name => "NAME_lc" });
my %hash;
my $sth = $db->prepare ("select week, month, workperiod from tablename
+");
$sth->execute;
while (my $rec = $sth->fetchrow_hashref) {
    $hash{$rec->{week}} = [ $rec->{month}, $rec->{workperiod} ];
    }
[download]