title: How can I store NULLs in NOT NULL field?
body: <p>I just came across NULL values in NOT-NULL fields in our test database. How could they get there? I know that NOT-NULL constraints can be altered with NOVALIDATE clause, but that would change table's last_ddl_time in USER_OBJECTS. And that time is less than the date that those records were created. Is there something else I'm overlooking? Or is that someone's manual work for sure?</p>
  
  <p>Table is partitioned and index-organized if that is relevant.
  Oracle version is 9.2</p>