ALTER TABLE `#__testquestions_sets`
  ADD COLUMN `parent_id` int unsigned NOT NULL DEFAULT 0 AFTER `id`,
  ADD COLUMN `set_type` varchar(12) NOT NULL DEFAULT 'ordinary' AFTER `parent_id`;

UPDATE `#__testquestions_sets`
SET `set_type` = 'ordinary'
WHERE `set_type` = '' OR `set_type` IS NULL;