MySQL time processing

SELECT DAY(date) as day_id,COUNT(*) FROM question_practice_detail 
WHERE MONTH(date)=8 and YEAR(date)=2021 
GROUP BY day_id 

#  insert data 
INSERT INTO  exam_record(uid, exam_id, start_time, submit_time,score)
values
(1001,9001,'2021-09-01 22:11:12','2021-09-01 23:01:12',90),
(1002,9002,'2021-09-04 07:01:02',null,null);

#  insert data 
INSERT INTO exam_record_before_2021
SELECT NULL,uid, exam_id, start_time, submit_time, score
FROM exam_record
WHERE submit_time < '2021-01-01 00:00:00';

replace into examination_info
(id,exam_id,tag,difficulty,duration,release_time)
values(null,9003,'SQL','hard',90,'2021-01-01 00:00:00')