try this , ill be interested to hear how it performs in comparison.

Note that the case statement on the call to GetRandomCode is required otherwise you will get the same value returned.

On my dev server it creates 15,000,000 rows in about 11 mins, cutting down the size of the union to your limited set should improve matters.

CREATE TABLE dbo.Numbers (Num INT NOT NULL PRIMARY KEY CLUSTERED);

GO

DECLARE @i INT;

SELECT @i = 1;

WHILE @i <= 10000

BEGIN

INSERT INTO dbo.Numbers(Num) VALUES (@i);

SELECT @i = @i + 1;

END;

Create View VwNewId

as

Select New_Id = newid()

go

Drop Function GetRandomCode

go

Create Function GetRandomCode(@CharsNeeded integer)

returns table

as

return

(

with cteCharsNeeded(Character)

as(

select '1' union all select '2' union all select '3' union all select '4' union all select '6' union all select '7' union all select '8' union all select '9' union all Select '0' union all

select 'A' union all select 'B' union all select 'C' union all select 'D' union all select 'E' union all select 'F' union all select 'G' union all select 'H' union all Select 'I' union all

select 'J' union all select 'K' union all select 'L' union all select 'M' union all select 'N' union all select 'O' union all select 'P' union all select 'Q' union all Select 'R' union all

select 'S' union all select 'T' union all select 'U' union all select 'V' union all select 'W' union all select 'X' union all select 'Y' union all select 'Z' union all

select 'a' union all select 'b' union all select 'c' union all select 'd' union all select 'e' union all select 'f' union all select 'g' union all select 'h' union all select 'i' union all

select 'j' union all select 'k' union all select 'l' union all select 'm' union all select 'n' union all select 'o' union all select 'p' union all select 'q' union all select 'r' union all

select 's' union all select 't' union all select 'u' union all select 'v' union all select 'w' union all select 'x' union all select 'y' union all select 'z'

),

ctenumbers(num)

as

(

Select Num from numbers

where Num <= @CharsNeeded

),

cteRandomChars(num,c)

as

(

select num,c = chars.c

from ctenumbers cross apply (select top 1 Character from cteCharsNeeded,vwNewId where num = num order by new_id) as chars(c)

)

select (

select c as [text()]

from cteRandomChars

for xml path('')) as Random

)

go

drop table #res

go

create table #res

(

random char(8)

)

insert into #res

select Random from sysobjects cross apply GetRandomCode(case when id is not null then 8 else null end)