一条SQL语句查询无限递归树所有数据

权限树：

SELECT PERMISSIONID, PARENTID, T.ITEMNAME,T.DESCRIPTION
  FROM T_PERMISSION T
 START WITH PARENTID =
            (SELECT PARENTID FROM T_PERMISSION WHERE PERMISSIONID = 0)
CONNECT BY PRIOR PERMISSIONID = PARENTID
 ORDER BY PARENTID

机构树：

SELECT AGENCYID, PARENTID, T.AGENCYNAME
  FROM T_AGENCY T
 START WITH PARENTID =
            (SELECT AGENCYID FROM T_AGENCY WHERE AGENCYID = 0)
CONNECT BY PRIOR AGENCYID = PARENTID
 ORDER BY PARENTID

以上是两个样例，而不是需要两个语句，只用一条语句即可。

定义数据库的时候需要定义一个ID和一个父ID，这样就可以形成无限递归树了。