declare @n varchar(64)

set @n='';

;with MyCTE1 as (
select N, newid() as rid from tally),
MyCte2 as (
select top(64) char(n%84+32) randchar from MyCTE1 order by rid)
select @n=@n+randchar
from MyCTE2

select @n

;with
a1 as (
select 1 as N union all select 1 union all select 1 union all select 1 union all
select 1 union all select 1 union all select 1 union all select 1
),
cteRandomString as (
select
	substring('0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ',(abs(checksum(newid()))%36)+1,1)
	as RandomString
from
	( select 1 as N from a1 as a cross join a1 as b ) a
)
select
	convert(varchar(64),replace((
	select
	    ','+RandomString
	from
	    cteRandomString
	for xml path (''))
	,',','')) as RandomString;

drop table #matt

declare @rows_needed int
declare @length_needed int

select @rows_needed=1000,
	@length_needed=64

select top(@rows_needed*@length_needed)
 identity(int,1,1) RN
,cast(N  as int) N
,0 as batchcol
,'' as randchar
 into #matt
 from tally
order by newid()

update #matt
set batchcol = cast(rn/@length_needed as int),
randchar = char(n%52+65)

create index m on #matt(batchcol) include(randchar)

select distinct batchcol,
(select 
	randchar as 'text()'
        from
            #matt m_in
           where m_in.batchcol=m_out.batchcol
        for xml path ('')) from #matt m_out