create table tb(fid varchar(50),fname varchar(50))
insert into tb select '51','四川'
insert into tb select '5101','成都'
insert into tb select '510101','锦江区'


create function getstr(@fid varchar(50))
returns varchar(500)
as
begin
declare @s varchar(500)
select @s=isnull(@s+'/','')+fname from tb where charindex(fid,@fid)>0 order by len(fid)
return @s
end

select fid,fname,dbo.getstr(fid) as fullname from tb

------解决方案--------------------
SQL code
--> 测试数据: T
if object_id('tempdb.dbo.T') is not null drop table T
create table T ([fID] int,[fName] varchar(6))
insert into T
select 51,'四川' union all
select 5101,'成都' union all
select 510101,'锦江区'
go
create/*--调用示例

------解决方案--------------------
估计函数可行,


------解决方案--------------------
SQL code
--> --> (Roy_88)生成測試數據
 
if not object_id('T') is null
    drop table T
Go
Create table T([fID] int,[fName] nvarchar(3))
Insert T
select 51,N'四川' union all
select 5101,N'成都' union all
select 510101,N'锦江区'
Go
create function F_str(@FID nvarchar(10))
returns nvarchar(1000)
as
begin
    declare @s nvarchar(1000) 
    select @s=''
    select @s=@s+'\'+[fName] from t where @FID like rtrim([FID])+'%' order by FID
return right(@s,len(@s)-1)
end
go
Select FID,FName=dbo.F_str(FID) from T

------解决方案--------------------
SQL code
--> --> (Ben)生成測試數據
 
if not object_id('Tempdb..#T') is null
    drop table #T
Go
Create table #T([fID] int,[fName] nvarchar(3))
Insert #T
select 51,'四川' union all
select 5101,'成都' union all
select 510101,'锦江区' union all
select 61,'湖南' union all
select 6101,'常德' union all
select 610101,'武陵区' 
Go
--Select * from #T
--
--我想查询出来成这样： 
--[fID]      [fName]      [fullName] 
--51          四川          四川 
--5101        成都          四川\成都 
--510101      锦江区        四川\成都\锦江区 


with tb as 
(
    select fid,fname,fullname=cast(fname as varchar) from #T where len(fid)=2
    union all
    select a.fid,a.fname,fullname=cast(tb.fullname+'\'+a.fname as varchar) from #T a ,tb 
    where a.fid like cast(tb.fid as varchar)+'%' and len(a.fid)-len(tb.fid)=2
)
select* from tb order by cast(fid as varchar)

--51        四川    四川
--5101        成都    四川\成都
--510101    锦江区    四川\成都\锦江区
--61        湖南    湖南
--6101        常德    湖南\常德
--610101    武陵区    湖南\常德\武陵区

------解决方案--------------------
--> 测试数据: T
if object_id('t_Area') is not null drop table t_Area
	create table t_Area (fID nvarchar(50),fName nvarchar(50))
insert into t_Area(fid,fname)
select 51,N'四川' union all
select 5101,N'成都' union all
select 510101,N'锦江区' union all
select 61,N'陕西' union all
select 6101,N'西安' union all
select 610101,N'雁塔区'

--取所需要的数据放入临时表
if OBJECT_ID('tempdb..#T') is not null drop table #T
	create table #T(FID nvarchar(20),FName nvarchar(50),FFullName NVarchar(100))
insert into #T(FID,FName,FFullName)
	select fid,FName,'' as FFullName
	from t_Area
	order by fid

declare @s nvarchar(100)
declare @v nvarchar(50)
set @s=''
set @v=null