SQL 时间函数minutes(),seconds(),timestampdiff()

数据
INSERT INTO exam_record(uid,exam_id,start_time,submit_time,score) VALUES
(1001, 9001, '2021-09-01 09:01:02', '2021-09-01 09:31:00', 81),
(1002, 9002, '2021-09-01 12:01:01', '2021-09-01 12:31:00', 70),
(1003, 9001, '2021-09-01 19:01:01', '2021-09-01 19:40:01', 86),
(1003, 9002, '2021-09-01 12:01:01', '2021-09-01 12:31:51', 89),
(1004, 9001, '2021-09-01 19:01:23', '2021-09-01 19:30:19', 85),
(1005, 9002, '2021-09-01 12:01:01', '2021-09-01 12:31:02', 85),
(1006, 9003, '2021-09-07 10:01:01', '2021-09-07 10:21:01', 84);

在做minute(submit_time-start_time)计算时，只要秒的位置：被减数的秒数大于减数的秒数，则返回null

 

也就是second、minute里的商不能显示负数，替换使用timestampdiff()则可以正常显示结果如下：