Re: diary constraints

On Aug 23, 2005, at 5:33 PM, Gary Stainburn wrote:

> I want to create a courtesy car diary diary system where I have a  
> table
> containing all of the cortesy cars in the pool, and then an allocation
> table which has two timestamps, one for the start date/time and one  
> for
> the return date/time.
>
> How do I go about creating constraints on inserts and updates to  
> ensure
> that
>
> a) the finish is after the start
> b) two allocations for a single vehicle don't overlap.

This is an interesting problem. You might want to take a look at this  
book, previously mentioned on the one of the lists (by George Essig,  
I believe):

> Developing Time-Oriented Database Applications in SQL
> by Richard T. Snodgrass
>
> The book is out of print, but the author has made the PDF available  
> on his website at:
> http://www.cs.arizona.edu/people/rts/tdbbook.pdf

Hope this helps!

Michael Glaesemann
grzm myrealbox com