http://www.cnblogs.com/exPlife/archive/2013/03/10/2952668.html
特别有用的是一个time转timestamp
select NOW();->2017-05-03 15:05:53
select NOW()+0; ->20170503150553
http://www.cnblogs.com/shihaiming/p/5853595.html datetime存毫秒的情况