protected function getDefaultConstraintName($xmldb_table, $xmldb_field) {

        // Get the quoted name of the table and field
        $tablename = $this->getTableName($xmldb_table);
        $fieldname = $xmldb_field->getName();

        // Look for any default constraint in this field and drop it
        if ($default = $this->mdb->get_record_sql("SELECT object_id, object_name(default_object_id) AS defaultconstraint
                                                     FROM sys.columns
                                                    WHERE object_id = object_id(?)
                                                          AND name = ?", array($tablename, $fieldname))) {
            return $default->defaultconstraint;
        } else {
            return false;
        }
    }