START WITH and CONNECT BY in Oracle SQL

select X, Lpad(' ', 2*(level-2))Rtrim(A) A
from test
start with X='XXX'
connect by prior X=Link
如需過濾階層可用Level 來過濾
Ex: 取到第2層
select X, Lpad(' ', 2*(level-2))Rtrim(A) A
from test1 start with X='XXX'
connect by prior X=Link
and Level = 2


http://www.adp-gmbh.ch/ora/sql/connect_by.html