Oracle中的Connect By... Start With语句实现了递归查询或者树状查询。
Connect By Prior 一方为起始（root）的ID
参考：
http://www.360doc.com/content/13/0422/16/11947209_280153192.shtml
http://www.oradev.com/connect_by.jsp
http://blog.csdn.net/haiross/article/details/17583725#t0
http://blog.csdn.net/haiross/article/details/17586565
Oracle ->> 层级查询语句（hierarchical query）connect by
原文：http://www.cnblogs.com/jenrrychen/p/4622549.html