Oracle数据库允许在什么情况下无效的datetime列值时间部分？

This case arises in a real-life situation where invalid data was in (and continuing to come into) an Oracle database which is extracted into a data processing system in Focus. Focus would choke and die on some rows with invalid time portions. The Oracle DBA would then go and copy the datetime into the affected column from a good column to allow the process to continue (yeah, I know).This case arises in a real-life situation where