moodle-mod_attendance/db/upgrade.php

<?php
// This file is part of Moodle - http://moodle.org/
//
// Moodle is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// Moodle is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.

/**
 * upgrade processes for this module.
 *
 * @package   mod_attendance
 * @copyright 2011 Artem Andreev <andreev.artem@gmail.com>
 * @license   http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */

/**
 * upgrade this attendance instance - this function could be skipped but it will be needed later
 * @param int $oldversion The old version of the attendance module
 * @return bool
 */
function xmldb_attendance_upgrade($oldversion=0) {

    global $CFG, $THEME, $DB;
    $dbman = $DB->get_manager(); // Loads ddl manager and xmldb classes.

    if ($oldversion < 2013082901) {
        $table = new xmldb_table('attendance_sessions');

        $field = new xmldb_field('studentscanmark');
        $field->set_attributes(XMLDB_TYPE_INTEGER, '1', XMLDB_UNSIGNED, XMLDB_NOTNULL, null, '0');
        if (!$dbman->field_exists($table, $field)) {
            $dbman->add_field($table, $field);
        }
        
        upgrade_mod_savepoint(true, 2013082901, 'attendance');
    }

    // UPGRADES from attforblock are only supported for sites that are running attforblock version 2012120700.
    return $result;
}