------解决方法--------------------------------------------------------,child varchar2(30));
insert into hier values(null,'Asia');
insert into hier values(null,'Australia');
insert into hier values(null,'Europe');
insert into hier values(null,'North America');
insert into hier values('Asia','China');
insert into hier values('Asia','Japan');
insert into hier values('Australia','New South Wales');
insert into hier values('New South Wales','Sydney');
insert into hier values('California','Redwood Shores');
insert into hier values('Canada','Ontario');
insert into hier values('China','Beijing');
insert into hier values('England','London');
insert into hier values('Europe','United Kingdom');
insert into hier values('Japan','Osaka');
insert into hier values('Japan','Tokyo');
insert into hier values('North America','Canada');
insert into hier values('North America','USA');
insert into hier values('Ontario','Ottawa');
insert into hier values('Ontario','Toronto');
insert into hier values('USA','California');
insert into hier values('United Kingdom','England');
那么我们可以使用START WITH . . . CONNECT BY . . .从句将父级地区与孩子地区连接起来，并将其层次等级显示出来。
--第一个sql语句
column child format a40
select level,lpad(' ',level*3)||child child
from hier
start with parent is null
connect by prior child = parent;
--第二个sql语句
column path format a50
select level,sys_connect_by_path(child,'/') path
from hier
start with parent is null
connect by prior child = parent;
