SELECT * FROM `subject` WHERE `postdate` >= ‘2015-03-06 ‘ AND `postdate` <= ‘2015-03-07‘
mysql 默认 的查询时间为：
SELECT * FROM `subject` WHERE `postdate` >= ‘2015-03-06 00:00:00 ‘ AND `postdate` <= ‘2015-03-07 00:00:00‘
原文：http://www.cnblogs.com/sunzhenyong/p/4318665.html