--生成测试数据
create table tTmp( id varchar(10), t2 varchar(100), t3 varchar(100), parentid varchar(10))
insert into tTmp
select '1', '12','13','0'
union all select '2', '22','23','1'
union all select '3', '32','33','2'

select * from tTmp
/*
id  t2  t3  parentid
1    12    13    0
2    22    23    1
3    32    33    2
*/

WITH cteTmp AS
(
    SELECT A.*, Convert(varchar(100),t2) as DetailName
    FROM tTmp AS A
    WHERE NOT EXISTS(SELECT * FROM tTmp WHERE id=A.parentid)
    UNION ALL 
    SELECT A.*, Convert(varchar(100),(A.t2 + B.DetailName)) AS DetailName
    FROM tTmp AS A
    JOIN cteTmp AS B
      ON A.parentid=B.id
)
SELECT id,t2,t3,parentid,DetailName+t3 as t2t3 FROM cteTmp 
order by DetailName;

/*
id  t2  t3  parentid  t2t3
1    12    13    0    1213
2    22    23    1    221223
3    32    33    2    32221233
*/

select * from tTmp
/*
id  t2  t3  parentid
1    12    13    0
2    22    23    1
3    32    33    2
*/

WITH cteTmp AS
(
    SELECT A.*, Convert(varchar(100),t2) as DetailName
    FROM tTmp AS A
    WHERE NOT EXISTS(SELECT * FROM tTmp WHERE id=A.parentid)
    UNION ALL 
    SELECT A.*, Convert(varchar(100),(A.t2 + B.DetailName)) AS DetailName
    FROM tTmp AS A
    JOIN cteTmp AS B
      ON A.parentid=B.id
)
update tTmp set tTmp.t2 = (select cteTmp.DetailName from cteTmp where tTmp.id = cteTmp.id)+ tTmp.t3

select * from tTmp
/*
id  t2  t3  parentid
1    1213    13    0
2    221223    23    1
3    32221233    33    2
*/

drop table tTmp;