Re: A foreign key on a self-referring table
Date: Sat, 06 Mar 2004 21:36:53 +0100
Message-ID: <404a3671$0$561$e4fe514c_at_news.xs4all.nl>
daveb wrote:
> "mAsterdam" <mAsterdam_at_vrijdag.org> wrote in message
> news:404a1860$0$573$e4fe514c_at_news.xs4all.nl...
>
>
>>+------------------+
>>| Reports_To |
>>+------+-----------+
>>| EMP# | MGR_EMP# |
>>+======+===========+
>>| 2 | 1 |
>>| 3 | 1 |
>>| 4 | 3 |
>>| 5 | 2 |
>>| 6 | 3 |
>>| 7 | 2 |
>>+------+-----------+
>>
>>, the predicate being
>>
>>"Employee with number (EMP#) reports to employee with number (MGR_EMP#)"
>>
>>Aside: There is a reason why I still would not have
>>this in a real database:
>>What if a managerspositon is vacant? But
>>that may be another topic.
>
> Well, it changes the functional dependencies; we now find that employees
> report to a department, not to a manager, and the OrganizationChart relates
> departments, not employees.