获得汉字字符串的首字母(T-SQL函数)

/*--获得汉字字符串的首字母--*/
if exists (select * from dbo.sysobjects where id = object_id(N'[dbo].[fGetPy]') and xtype in (N'FN', N'IF', N'TF'))
drop function [dbo].[fGetPy]
GO

--创建取拼音函数
create function fGetPy(@Str varchar(500)='')
returns varchar(500)
as
begin--函数实现开始

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--while循环开始
select @ii=@ii+1,@n=63,@chn=substring(@str,@ii,1)

if @chn>'z'--if开始
--此处只有一个 select 语句，原理以“字符串排序以及ASCII码表”：
select @n = @n +1,@c = --★★★select★★★
case chn --case开始
when @chn then char(@n) --case分支
else @c --case分支
end --case结束
from( --★★★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 --if对应的else
set @c=@chn
--if结束

set @return=@return+@c
end--while循环结束

return(@return)
end--函数实现结束

go
--测试
select dbo.fgetpy('魏保光') as 姓名拼音,dbo.fgetpy('ab中c国人') as 中国人
select dbo.fgetpy('刘子良') as 姓名拼音,dbo.fgetpy('ab中c国人') as 中国人
select dbo.fgetpy('吴过') as 姓名拼音,dbo.fgetpy('ab中c国人') as 中国人
select dbo.fgetpy('东北') as 姓名拼音,dbo.fgetpy('ab中c国人') as 中国人
select dbo.fgetpy('王大海八丫') as 王大海八丫,dbo.fgetpy('服務地圖') as 服務地圖

--删除拼音函数
drop function fgetpy