http://www.cnblogs.com/2018/archive/2011/11/22/2240259.html
http://wenku.baidu.com/link?url=LSqlCiqi_O_1VwSRTrK7WEak4kV9O492xkZsw24DK2ScCSNMDMbT9TFw82tyD9Sj2dyWPgz83aYBkFYz92Gp1ODee7f3s4slE5D7dGJiVZW