mysql表中datetime类型的字段名createtime，查询所有createtime为空的语句如下：
select * from yy_business where ISNULL(createtime) is TRUE
update yy_business set createtime=‘2015-01-21 17:24:58‘ where ISNULL(createtime) is TRUE
原文：http://www.cnblogs.com/sdfiggtx/p/5158888.html