$sth = $dbh->prepare("select COLUMN_1 from table where COLUMN_2 < 2500");
$sth->execute();

while (my ($column_1_value) = $sth->fetchrow_array()) {

# do some processing on the column 1 value here

}

##</code><code>##


$sth = $dbh->prepare("select COLUMN_1 from table where COLUMN_2 between ? and ?");

for ($i = 0; $i < 2500; $i += 100) {

    $sth->execute($i, $i + 100);

    while (my ($column_1_value) = $sth->fetchrow_array()) {

        # do some processing on the column 1 value here

    }

}