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 22:11:12' + INTERVAL 50 minute, 90 ), (NULL, 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 22:11:12' + INTERVAL 50 minute, 90 ), (NULL, 1002, 9002, '2021-09-04 07:01:02', NULL, NULL);