用datediff函数，第一个参数是截止时间，第二个参数是起始时间 ~~~ select datediff('2009-1-1', '2008-1-1'); ~~~ 将时间日期`datetime`字段和某日期比较 ~~~ select count(*) as count from l_register where DATEDIFF(`createtime`,'2017-11-24') = 0 limit 1 ~~~