mysql:group_concat
http://www.cnblogs.com/wenxinphp/p/5841430.html
mysql:find_in_set
http://www.cnblogs.com/manongxiaobing/p/4682698.html
oracle:树操作
http://www.cnblogs.com/linjiqin/archive/2013/06/24/3152674.html
http://www.cnblogs.com/chen1388/archive/2010/09/25/1834827.html
http://www.cnblogs.com/quanweiru/archive/2012/11/18/2775843.html
http://blog.csdn.net/nimeijian/article/details/50231851
mysql实现oracle树查询: