In Netezza you can use LPAD:
select lpad(s.sample,10,0) as result
from (select 12345 as sample) s
result
-------
0000012345
However it would be more efficient to remove the zeros like in the example below:
select cast(trim(Leading '0' from s.sample) as integer) as result
from (select '0000012345' as sample) s
result
-------
12345