> I have a business rule which gives me rahter big challenges to "melt
> in SQL":
>
> At one "point in time" only one version may be active.
I have no specific solution, but I highly recommend Richard Snodgrass's
book, Developing Time-Oriented Database Applications in SQL, which
discusses this kind of situation, and many other similar ones. It's
out of print, but available from his homepage as a PDF:
http://www.cs.arizona.edu/~rts/
- John D. Burger
MITRE