select t4.emp_id, t4.emp_level, t4.tag as exam_tag from (select t1.emp_id, t2.emp_level, t3.tag, t1.exam_id, t1.submit_time-t1.start_time as time, t1.score from exam_record t1 left join emp_info t2 on t1.emp_id=t2.emp_id left join examination_info t3 on t1.exam_id=t3.exam_id where t2.emp_level<7)...