SQL SERVER 得到汉字首字母函数四版全集 --【叶子】

--创建取汉字首字母函数(第三版)
create function [dbo].[f_getpy_V3]
(
    @col varchar(1000)
)
returns varchar(1000)
as
    begin
        declare @cyc int,@len int,@sql varchar(1000),@char varbinary(20)
        select @cyc = 1,@len = len(@col),@sql = ''
        while @cyc <= @len
            begin
                select @char = cast(substring(@col, @cyc, 1) as varbinary)
                declare @maco table (bcode varbinary(20),ecode varbinary(20),letter varchar(10))
                insert into @maco
                select 0XB0A1,0XB0C4,'A' union all
                select 0XB0C5,0XB2C0,'B' union all
                select 0XB2C1,0XB4ED,'C' union all
                select 0XB4EE,0XB6E9,'D' union all
                select 0XB6EA,0XB7A1,'E' union all
                select 0XB7A2,0XB8C0,'F' union all
                select 0XB8C1,0XB9FD,'G' union all
                select 0XB9FE,0XBBF6,'H' union all
                select 0XBBF7,0XBFA5,'J' union all
                select 0XBFA6,0XC0AB,'K' union all
                select 0XC0AC,0XC2E7,'L' union all
                select 0XC2E8,0XC4C2,'M' union all
                select 0XC4C3,0XC5B5,'N' union all
                select 0XC5B6,0XC5BD,'O' union all
                select 0XC5BE,0XC6D9,'P' union all
                select 0XC6DA,0XC8BA,'Q' union all
                select 0XC8BB,0XC8F5,'R' union all
                select 0XC8F6,0XCBF9,'S' union all
                select 0XCBFA,0XCDD9,'T' union all
                select 0XCDDA,0XCEF3,'W' union all
                select 0XCEF4,0XD1B8,'X' union all
                select 0XD1B9,0XD4D0,'Y' union all
                select 0XD4D1,0XD7F9,'Z'
                select top 1 @sql=@sql+letter from @maco where @char between bcode and ecode
                set @cyc = @cyc + 1
            end
        return @sql
    end
go
--创建取汉字首字母函数(第四版)
create function [dbo].[f_getpy_V4]
(
    @col varchar(1000)
)
returns varchar(1000)
    begin
        declare @cyc int,@len int,@sql varchar(1000),@char varbinary(20)
        select @cyc = 1,@len = len(@col),@sql = ''
        while @cyc <= @len
            begin
                select @char = cast(substring(@col, @cyc, 1) as varbinary)
                if @char>=0XB0A1 and @char<=0XB0C4      set @sql=@sql+'A'
                else if @char>=0XB0C5 and @char<=0XB2C0 set @sql=@sql+'B'
                else if @char>=0XB2C1 and @char<=0XB4ED set @sql=@sql+'C'
                else if @char>=0XB4EE and @char<=0XB6E9 set @sql=@sql+'D'
                else if @char>=0XB6EA and @char<=0XB7A1 set @sql=@sql+'E'
                else if @char>=0XB7A2 and @char<=0XB8C0 set @sql=@sql+'F'
                else if @char>=0XB8C1 and @char<=0XB9FD set @sql=@sql+'G'
                else if @char>=0XB9FE and @char<=0XBBF6 set @sql=@sql+'H'
                else if @char>=0XBBF7 and @char<=0XBFA5 set @sql=@sql+'J'
                else if @char>=0XBFA6 and @char<=0XC0AB set @sql=@sql+'K'
                else if @char>=0XC0AC and @char<=0XC2E7 set @sql=@sql+'L'
                else if @char>=0XC2E8 and @char<=0XC4C2 set @sql=@sql+'M'
                else if @char>=0XC4C3 and @char<=0XC5B5 set @sql=@sql+'N'
                else if @char>=0XC5B6 and @char<=0XC5BD set @sql=@sql+'O'
                else if @char>=0XC5BE and @char<=0XC6D9 set @sql=@sql+'P'
                else if @char>=0XC6DA and @char<=0XC8BA set @sql=@sql+'Q'
                else if @char>=0XC8BB and @char<=0XC8F5 set @sql=@sql+'R'
                else if @char>=0XC8F6 and @char<=0XCBF9 set @sql=@sql+'S'
                else if @char>=0XCBFA and @char<=0XCDD9 set @sql=@sql+'T'
                else if @char>=0XCDDA and @char<=0XCEF3 set @sql=@sql+'W'
                else if @char>=0XCEF4 and @char<=0XD1B8 set @sql=@sql+'X'
                else if @char>=0XD1B9 and @char<=0XD4D0 set @sql=@sql+'Y'
                else if @char>=0XD4D1 and @char<=0XD7F9 set @sql=@sql+'Z'
                set @cyc = @cyc + 1
            end
        return @sql
    end
go
--创建取汉字首字母函数(第一版)
create function [dbo].[f_getpy_V1] (@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)
       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

go
--创建取汉字首字母函数(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

--思路基本是一样的，但是不同类型导致效率上有差别，这个差别不同环境测试出来的效果竟然不一样。 

select dbo.f_getpy_V1('我是一个土生土长的中国人')
select dbo.f_getpy_V2('我是一个土生土长的中国人')
select dbo.f_getpy_V3('我是一个土生土长的中国人')
select dbo.f_getpy_V4('我是一个土生土长的中国人') 

--我现在测试到的开销百分比是：
--1:2:3:4 对应 18%:38%:44%:0%

--如果你感兴趣也可以在本地测试一下，看看执行计划，这4个函数哪个最高效呢？可以把开销百分比留言在下面，谢谢！