生成父子关系树形模型数据

with t as
(select 'a'c1,'b'c2,'c'c3 from dual union
select 'a','b','d' from dual union
select 'a','e','f' from dual),
t1 as
(select c1,c2 from t
union
select c2,c3 from t),
t2 as
(select c1 from t1
union
select c2 from t1),
t3 as
(select c1,rownum rn from(select c1 from t2 order by c1)),
t4 as
(select a.*,b.c1 p from t3 a left join t1 b on(a.c1=b.c2))
select x.c1,x.rn,nvl(y.rn,0)prn from t4 x left join t3 y on(x.p=y.c1) order by 1;