text: DELETE FROM `wp_attribute` WHERE model_id = (SELECT id FROM wp_model WHERE `name`='exam' ORDER BY id DESC LIMIT 1);
  DELETE FROM `wp_model` WHERE `name`='exam' ORDER BY id DESC LIMIT 1;
  DROP TABLE IF EXISTS `wp_exam`;
  
  DELETE FROM `wp_attribute` WHERE model_id = (SELECT id FROM wp_model WHERE `name`='exam_question' ORDER BY id DESC LIMIT 1);
  DELETE FROM `wp_model` WHERE `name`='exam_question' ORDER BY id DESC LIMIT 1;
  DROP TABLE IF EXISTS `wp_exam_question`;
  
  DELETE FROM `wp_attribute` WHERE model_id = (SELECT id FROM wp_model WHERE `name`='exam_answer' ORDER BY id DESC LIMIT 1);
  DELETE FROM `wp_model` WHERE `name`='exam_answer' ORDER BY id DESC LIMIT 1;
  DROP TABLE IF EXISTS `wp_exam_answer`;