select * from order where create_time>'2016-05-21 00:00:00'; 不包含2016-05-21 00:00:00时的订单

select * from order where create_time>'2016-05-21'; 包含2016-05-21 00:00:00时的订单

等价于

select * from order where create_time>='2016-05-21 00:00:00';