1、自頂向下查找
select t.name, t.id from tree t start with t.id = 'top' CONNECT BY PRIOR t.id = t.parent_id order SIBLINGS by t.order_no
2、自底向上查找
select t.name, t.id from tree t start with t.id = 'top' CONNECT BY PRIOR t.parent_id = t.id order SIBLINGS by t.order_no