Re: 3 value logic. Why is SQL so special?
Date: 13 Sep 2006 14:20:16 -0700
Message-ID: <1158182415.999763.116660_at_e3g2000cwe.googlegroups.com>
Anne & Lynn Wheeler wrote:
> there is also, always the possibility that you might have an
> unscheduled actual flight ... an unplanned flight for which there
> hadn't been a (pre-)scheduled departure/arrival ... but for which
> there is actual departure ... with initially a projected arrival (as
> opposed to a scheduled arrival) ... and then eventually an actual
> arrival.
See proposed schema...
ANY unscheduled departure is still a FLIGHT before being a new DEPARTURE. A new DEPARTURE line should be added IF AND ONLY IF the plane leaves from a specific AIRPORT at a SPECIFIC TIME to SOME SUPPOSED AIRPORT and SOME SUPPOSED ARRIVAL TIME which is nessecarily what constitutes a FLIGHT. 2 inserts instead of one...That way such the FLIGHT can be unscheduled only ONCE.
Note: been putting caps for emphasis. No hostile intent. ;) Received on Wed Sep 13 2006 - 23:20:16 CEST