详见原文博客链接 http://www.killdb.com/2011/11/06/%e5%bf%98%e8%ae%b0oracle-%e7%94%a8%e6%88%b7%e5%af%86%e7%a0%81%e6%80%8e%e4%b9%88%e5%8a%9e%ef%bc%9f.html
