请教: 怎样把ID与它的父ID串起来？？？？？

请问怎样把ID与它的父ID串起来？我要得到的效果是：
a,b,c,e,g,j
a,b,c,e,g,k
a,c，e
表如下：create table test(ID varchar(10),fuID varchar(10))insert into test
select 'a','' union
select 'b','a' union
select 'c','a' union
select 'd','b' union
select 'e','c' union
select 'f','d' union
select 'g','e' union
select 'h','f' union
select 'i','f' union
select 'j','g' union
select 'k','g'