各种数据库的数据类型对比
postgresql sqlite sqlserver sybase db2 mysql openbase oracle binary bytea blob image image blob(32768) blob object blob boolean boolean boolean bit bit decimal(1) tinyint(1) boolean number(1) date date date datetime datetime date date date date datetime timestamp datetime datetime datetime timestamp datetime datetime date decimal decimal decimal decimal decimal decimal decimal decimal decimal float float float float(8) float(8) float float float number integer integer integer int int int int(11) integer number(38) string (note 1) varchar(255) varchar(255) varchar(255) varchar(255) varchar(255) char(4096) varchar2(255) text text text text text clob(32768) text text clob time time datetime datetime time time time time date timestamp timestamp datetime datetime timestamp timestamp datetime timestamp date

reference:
http://www.blogjava.net/GavinMiao/archive/2011/09/06/358081.html
http://blog.csdn.net/dengxingbo/article/details/5896314
http://onlamp.com/onlamp/2001/09/13/aboutSQL.html
http://www.java2s.com/Code/Java/Hibernate/JavaTypeVSHibernateType.htm