WITH t AS (
    SELECT exam_id, AVG(TIMESTAMPDIFF(MINUTE,start_time,submit_time)) AS avg_time,
           avg(score) AS avg_score
    FROM exam_record 
    GROUP BY exam_id
)
SELECT t1.emp_id,t1.emp_level,t3.tag AS exam_tag
FROM emp_info t1 
LEFT JOIN exam_record  t2 ON t1.emp_id=t2.emp_id
LEFT JOIN examination_info t3 ON t2.exam_id=t3.exam_id
LEFT JOIN t ON t.exam_id=t2.exam_id
WHERE t1.emp_level<7 AND TIMESTAMPDIFF(MINUTE,t2.start_time,t2.submit_time)<t.avg_time AND t2.score>t.avg_score
ORDER BY emp_id