1、date() 返回日期部分

    select * from contract where date(add_time) = '2014-04-26'

2、统计3月份的文件

    select count(*) from attachment where date(add_time) between '2014-03-01' and '2014-03-31'

    或者

   select count(*) from attachment where year(add_time) = 2014 and month(add_time) = 3

3、统计7天之内的文件(返回两个日期之间的天数,参数1-参数2)

    select count(*) from attachment where datediff(add_time,now()) >=0 and datediff(add_time,now()) < 7

4、时间差(返回值示例08:08:08)

   timediff(now(),add_time) 

5、日期加减

    set @dt = now();