树的查询

1，查所有的子节点 select  *  from wz_tree   start with id = 1 connect by prior id = pid;
2，查所有的父节点  select  *  from wz_tree   start with id = 256 connect by prior pid = id;
3，查分类的路径, 用逗号连接:select  sys_connect_by_path(mc, ',')   from wz_tree   start with id = 1 connect by prior id = pid;http://www.itpub.net/838127.html讲的很详细
4，查某个表的字段名:
select max(substr(SYS_CONNECT_BY_PATH(COLUMN_NAME, ','), 2)) col
  from (select COLUMN_NAME, column_id
          from user_tab_columns
         where table_name = '&TEST')--&为plsqldeveloper里的字符串占位符,执行时会弹出对话框让你填值
 start with column_id = 1
connect by column_id = rownum;

5，select  *  from wz_tree where mc like '%五金'  start with id = 1 connect by prior id = pid;
和select  *  from wz_tree start with id = 1 connect by prior id = pid and mc like '%五金' 
二者的查询结果不一样