SQL Server ->> Move characters in string N position(s) forward/backward based on ASCII table(根据ASCII表的排列顺序将字符串内的数值往前或者后移N个位)

去年无聊的时候想到想玩一下根据ASCII表的排列顺序将字符串内的数值往前或者后移N个位，顺便看一下是T-SQL性能好还是用C#写CLR函数处理得快。结果是在50万行以下其实两者差距很小，当然这是在我的笔记本上测试的结果（I5双核四线程+8G内存+5600转的机械硬盘）。在100万行以上的时候用T-SQL基于集合的方式就体现出优势了，用了大概1分多钟就处理完100万行，而CLR用了4分多钟还没处理完。这里贴上当时的T-SQL代码。

if OBJECT_ID('tempdb..#tt') is not null
    drop table #tt

if OBJECT_ID('tempdb..#t') is not null
    drop table #t

if OBJECT_ID('tempdb..#ttt') is not null
    drop table #ttt

if OBJECT_ID('tempdb..#tttt') is not null
    drop table #tttt

select dbo.tblNumbers.id, abs(CHECKSUM(NEWID()))%62 as fld1,
           abs(CHECKSUM(NEWID()))%62 as fld2,
           abs(CHECKSUM(NEWID()))%62 as fld3,
           abs(CHECKSUM(NEWID()))%62 as fld4,
           abs(CHECKSUM(NEWID()))%62 as fld5,
           abs(CHECKSUM(NEWID()))%62 as fld6,
           abs(CHECKSUM(NEWID()))%62 as fld7,
           abs(CHECKSUM(NEWID()))%62 as fld8,
           abs(CHECKSUM(NEWID()))%62 as fld9,
           abs(CHECKSUM(NEWID()))%62 as fld10,
           abs(CHECKSUM(NEWID()))%62 as fld11,
           abs(CHECKSUM(NEWID()))%62 as fld12,
           abs(CHECKSUM(NEWID()))%62 as fld13,
           abs(CHECKSUM(NEWID()))%62 as fld14,
           abs(CHECKSUM(NEWID()))%62 as fld15,
           abs(CHECKSUM(NEWID()))%62 as fld16 into #tt
from dbo.tblNumbers
WHERE ID<= 100000;

select [str], ROW_NUMBER() over(order by CHECKSUM(NEWID()))-1 as rn into #t
from (select CHAR(ID+64) as [str] from dbo.tblNumbers where ID <= 26 union all
      select CHAR(ID+96) as [str] from dbo.tblNumbers where ID <= 26 union all
      select cast(ID-1 as varchar) as [str] from dbo.tblNumbers where ID <= 10) as t

select tt.ID, left(t1.str + t2.str + t3.str + t4.str + t5.str + t6.str + t7.str + t8.str +
              t9.str + t10.str + t11.str + t12.str + t13.str + t14.str + t15.str + t16.str + REPLICATE(' ',1000),1000) as result
into #tttt
from #tt as tt join
        #t t1 on t1.rn = tt.fld1 join
        #t t2 on t2.rn = tt.fld2 join
        #t t3 on t3.rn = tt.fld3 join
        #t t4 on t4.rn = tt.fld4 join
        #t t5 on t5.rn = tt.fld5 join
        #t t6 on t6.rn = tt.fld6 join
        #t t7 on t7.rn = tt.fld7 join
        #t t8 on t8.rn = tt.fld8 join
        #t t9 on t9.rn = tt.fld9 join
        #t t10 on t10.rn = tt.fld10 join
        #t t11 on t11.rn = tt.fld11 join
        #t t12 on t12.rn = tt.fld12 join
        #t t13 on t13.rn = tt.fld13 join
        #t t14 on t14.rn = tt.fld14 join
        #t t15 on t15.rn = tt.fld15 join
        #t t16 on t16.rn = tt.fld16

checkpoint
DBCC DROPCLEANBUFFERS
DBCC FREESYSTEMCACHE('all') 

select dbo.ufn_MoveCharacterBackOrForwardByNPos(result,'forward',1), result from #tttt
select dbo.ufn_clr_MoveCharacterBackOrForwardByNPos(result,'forward',1), result from #tttt

select dbo.ufn_MoveCharacterBackOrForwardByNPos('oOv3lVLo4W3B44L7','forward',1)
select dbo.ufn_clr_MoveCharacterBackOrForwardByNPos('oOv3lVLo4W3B44L7','forward',1)

declare @int as int = 1;
declare @cmd as varchar(max) = '';
declare @cmdd as varchar(max) = '';
declare @comand as varchar(max) = '';
declare @comandd as varchar(max) = '';

--select ISNULL(NULLIF(0,0),26)

--select @@VERSION
while @int <= 101
begin
    set @cmd = @cmd + 'substring(result,'+CAST(@int as varchar)+',1) as fld' +CAST(@int as varchar) + ','
    set @cmdd = @cmdd + 'case when ASCII(fld' +CAST(@int as varchar) + ') between 65 and 90 then CHAR(ISNULL(NULLIF((ASCII(fld' +CAST(@int as varchar) + ')-64+1)%26,0),26)+64)
                              when ASCII(fld' +CAST(@int as varchar) + ') between 97 and 122 then CHAR(ISNULL(NULLIF((ASCII(fld' +CAST(@int as varchar) + ')-64+1)%26,0),26)+64)
                              when fld' +CAST(@int as varchar) + ' like ''[0-9]'' then CHAR(ISNULL(NULLIF((ASCII(fld' +CAST(@int as varchar) + ')-47+1)%10,0),10)+47)
                              else fld' +CAST(@int as varchar) + ' end +';

    if LEN(@cmd) > 7950
    begin
        set @comand = @comand + cast(@cmd as varchar(max))
        set @cmd = '';
    end

    if LEN(@cmdd) > 7950
    begin
        --print len(@cmdd)
        set @comandd = @comandd + cast(@cmdd as varchar(max))
        set @cmdd = '';
    end

    set @int = @int + 1
end
--select @cmdd
if LEN(@cmd) > 0
    set @comand = 'select rtrim(result) AS result,' + @comand + cast(left(@cmd,len(@cmd)-1) as varchar(max)) + '
    from #tttt as a'
--select @cmdd, LEN(@cmdd)
--select @comandd, LEN(@cmdd)
if LEN(@cmdd) > 0
    set @comandd = 'select rtrim(' + @comandd + cast(left(@cmdd,len(@cmdd)-1) as varchar(max)) + ') as final_str, result
                    from (' + @comand + ') as t'

--select @comandd
EXEC( @comandd)

--select * from #ttt

CREATE TYPE udt_TwoCharacterColumn8000Long
AS TABLE (
    col1 VARCHAR(8000) NULL,
    col2 VARCHAR(8000) NULL
)

alter PROCEDURE usp_UDTtest
    @t as udt_TwoCharacterColumn8000Long readonly
as
select * from @t

declare @a as udt_TwoCharacterColumn8000Long

insert into @a
select 'abc', 'def'

exec usp_UDTtest @a