# Update oid with new timestamp
my $sql = <<"EOT";
update clock
 set time = ?
where oid = ?
EOT

my $upd_h = $dbh->prepare($sql);
$upd_h->execute($new_time, $oid);

# Get oid(s) with latest timestamp
# This could all be done in one select
# with either a subquery or ordering
# by descending time, but this is one way

# Get max timestamp
$sql = <<"EOT";
select max(time)
from clock
EOT

my ($time) = @{$dbh->selectcol_arrayref($sql)};

# Get all oid(s) with max timestamp
$sql = <<"EOT";
select oid
from clock
where time = ?
EOT

my (@oids) = @{$dbh->selectcol_arrayref($sql, {}, $time);
[download]