Code:
Update FILE1
set csfill = (substr(csfill,1,37) || 'N' || substr(csfill,39,12)
where FILE1/cstno in (
select FILE2/cscstn
from FILE2
where ORDERTYPE = 'FE'
or ORDERTYPE = 'CE')
and substr(csfill,38,1) = 'Y'

