with cteRandoms
as(

select top 10000 abs(checksum(NewId()))%600 as Random , ROW_NUMBER() over (order by (select null)) as RowN
 from  syscolumns a cross join syscolumns b
),
ctefilter
as
(
select * ,row_number() over (partition by Random order by RowN ) Rowfilter from cteRandoms
)
select top 300 Random 
from ctefilter 
where Rowfilter < 3
order by RowN

 select Random
   from numbers
  cross apply GetVariableLengthRandomCode(ISNULL(8,num),16,'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789')