sql 语句 提取中文的首字母

create function f_GetPy(@str nvarchar(4000))
returns nvarchar(4000)
as
begin
declare @strlen int,@re nvarchar(4000)
declare @t table(chr nchar(1) collate Chinese_PRC_CI_AS,letter nchar(1))
insert into @t(chr,letter)
  select '吖','A' union all select '八','B' union all
  select '嚓','C' union all select '咑','D' union all
  select '妸','E' union all select '发','F' union all
  select '旮','G' union all select '铪','H' union all
  select '丌','J' union all select '咔','K' union all
  select '垃','L' union all select '嘸','M' union all
  select '拏','N' union all select '噢','O' union all
  select '妑','P' union all select '七','Q' union all
  select '呥','R' union all select '仨','S' union all
  select '他','T' union all select '屲','W' union all
  select '夕','X' union all select '丫','Y' union all
  select '帀','Z'
  select @strlen=len(@str),@re=''
  while @strlen>0
  begin
    select top 1 @re=letter+@re,@strlen=@strlen-1
      from @t a where chr<=substring(@str,@strlen,1)
      order by chr desc
    if @@rowcount=0
      select @re=substring(@str,@strlen,1)+@re,@strlen=@strlen-1
  end
  return(@re)
end
go

--先执行上述语句然后调用
select dbo.f_GetPy('中国')