create table AAA(ID INT,strNum1 varchar(8),strNum2 varchar(8),intTaxis int) 
insert into AAA select 1,'01' ,'001',1
insert into AAA select 2,'001','011',2 
insert into AAA select 3,'001','010',1 
insert into AAA select 6,'01' ,'002',2 
insert into AAA select 4,'002','021',1 
insert into AAA select 5,'002','022',2 
go

--创建用户定义函数
create function f_getChild(@strNum1 VARCHAR(10))
returns @t table(strNum1 VARCHAR(10),strNum2 VARCHAR(10),Level INT,Ord varchar(100))
as
begin
    declare @i int
    set @i=1
    insert into @t select strNum1,strNum2,@i,right('0'+strNum2,3) from AAA where strNum1 = @strNum1
    
    while @@rowcount<>0
    begin
        set @i=@i+1
        insert into @t 
        select 
            a.strNum1,a.strNum2,@i,b.Ord+a.strNum2
        from 
            AAA a,@t b 
        where 
            a.strNum1=b.strNum2 and b.Level=@i-1
            and
            not exists(select 1 from @t where strNum1=a.strNum1 and strNum2=a.strNum2)
    end
    return
end
go

--执行查询
select * from dbo.f_getChild('01') order by Ord
go

--输出结果
/*
strNum1    strNum2    Level       Ord
---------- ---------- ----------- -----------
01         001        1           001
001        010        2           001010
001        011        2           001011
01         002        1           002
002        021        2           002021
002        022        2           002022
*/

--删除测试数据
drop function f_getChild
drop table AAA
go