Sqlserver得到汉字拼音首字母存储过程

Sqlserver得到汉字拼音首字母存储过程:
create function [dbo].[fun_getPY]
(
@str nvarchar(4000)
)
returns nvarchar(4000)
as
begin
declare @word nchar(1),@PY nvarchar(4000)
set @PY=''
while len(@str)>0
begin
   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'骜' as word
               union all select 'B',N'簿'
               union all select 'C',N'错'
               union all select 'D',N'鵽'
               union all select 'E',N'樲'
               union all select 'F',N'鳆'
               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'
    &nb