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

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 into exam_record (id,uid,exam_id,start_time,submit_time,score)

VALUES(null,1001,9001,'2021-09-01 22:11:12','2021-09-01 23:01:12',90),

(null,1002,9002,'2021-09-04 7:01:02',null,null)