mysql可以比较时间吗

INSERT INTO t1 (testdate) VALUES (20180912);

INSERT INTO t1 (testdate) VALUES ('20180912');

INSERT INTO t1 (testdate) VALUES ('18-09-12');

INSERT INTO t1 (testdate) VALUES ('2018.09.12');

INSERT INTO t1 (testdate) VALUES ('2018 09 12');

INSERT INTO t1 (testdate) VALUES ('0000-00-00');

SELECT testdate FROM t1 WHERE testdate >= '2018-09-12';

SELECT testdate FROM t1 WHERE testdate >= 20180912;

SELECT MOD(testdate,100) FROM t1 WHERE testdate >= 20180912;

SELECT testdate FROM t1 WHERE testdate >= '20180912';

select meeting_id,meeting_name,start_time,end_time from meeting_data

    where meeting_id REGEXP '[0-9]{4}0001'

        and unix_timestamp(start_time) < unix_timestamp(NOW())

        and unix_timestamp(end_time) > unix_timestamp(NOW());