mssql 中文转拼音首字母

在做列车时刻表进行搜索时用到中文转拼音首字母时需要以下函数

Create  function 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'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)
  end

  return @PY

end

--测试
select dbo.fun_getPY('t北京大学医学部')