Try this one. It will generate all the update statements for 1 database, without any objects in the sys scheme.



Code:
select  replace(replace('update [TABLE] set [COLUMN] = NULL where len([COLUMN]) = 0', '[TABLE]', t.name), '[COLUMN]', c.name)
from    sys.columns c
        inner join sys.tables t
          on  t.object_id = c.object_id
          and t.schema_id <> 4