sql取字符串的首字母的函数

如 
火炬    返回 'H'
yuji2008 返回 'Y'
假如首位是数字或特殊字符，就直接返回首位
如：
3535sfsf  返回'3'
#$%sfsdf43646  返回'#'

返回大写字母，要求要用sql server 2000函数写

create  function [dbo].[chinese_firstletter]
(
  @str nvarchar(1)
)
returns nvarchar(1)
as
begin
  declare @word nchar(1),@PY nvarchar(4000)
  set @PY=''

    set @word=left(@str,1)
    --如果非汉字字符，返回原字符
    set @PY=@PY+(case when unicode(@word) between 19968 and 19968+20901
                    then ( 
                    select top 1 PY from 
                    ( 
                    select 'A' as PY,N'驁' as word
                    union all select 'B',N'簿'
                    union all select 'C',N'錯'
                    union all select 'D',N'鵽'
                    union all select 'E',N'樲'
                    union all select 'F',N'鰒'
                    union all select 'G',N'腂'
                    union all select 'H',N'夻'
                    union all select 'J',N'攈'
                    union all select 'K',N'穒'
                    union all select 'L',N'鱳'
                    union all select 'M',N'旀'
                    union all select 'N',N'桛'
                    union all select 'O',N'漚'
                    union all select 'P',N'曝'
                    union all select 'Q',N'囕'
                    union all select 'R',N'鶸'
                    union all select 'S',N'蜶'
                    union all select 'T',N'籜'
                    union all select 'W',N'鶩'
                    union all select 'X',N'鑂'
                    union all select 'Y',N'韻'
                    union all select 'Z',N'咗' ) T where word>=@word collate Chinese_PRC_CS_AS_KS_WS 
                    order by PY ASC
                          ) 
                    else @word 
                end)
    set @str=right(@str,len(@str)-1)

  return @PY
end

go

Select dbo.chinese_firstletter('福田区第五医院')

drop function chinese_firstletter