sql server获取汉字首字母的函数(第二版)

---取得汉字首字母函数(第二版)
create function [dbo].[f_getpy_V2](@Str varchar(500)='')
    returns varchar(500)
    as
    begin
        declare @strlen int,@return varchar(500),@ii int
        declare @n int,@c char(1),@chn nchar(1)
        select @strlen=len(@str),@return='',@ii=0
        set @ii=0
        while @ii<@strlen
        begin
           select @ii=@ii+1,@n=63,@chn=substring(@str,@ii,1)
           if @chn>'z'
           select @n = @n +1
           ,@c = case chn when @chn then char(@n) else @c end
           from(
           select top 27 * from (
           select chn = '吖'
           union all select '八'
           union all select '嚓'
           union all select '咑'
           union all select '妸'
           union all select '发'
           union all select '旮'
           union all select '铪'
           union all select '丌' --because have no 'i'
           union all select '丌'
           union all select '咔'
           union all select '垃'
           union all select '嘸'
           union all select '拏'
           union all select '噢'
           union all select '妑'
           union all select '七'
           union all select '呥'
           union all select '仨'
           union all select '他'
           union all select '屲' --no 'u'
           union all select '屲' --no 'v'
           union all select '屲'
           union all select '夕'
           union all select '丫'
           union all select '帀'
           union all select @chn) as a
           order by chn COLLATE Chinese_PRC_CI_AS
           ) as b
           else set @c='a'
           set @return=@return+@c
        end
        return(@return)
    end