Pete,

first of all I'd like to thank everybody who answered the thread.

If I didn't answer before it was because I was under shock.

If further thinking won't produce any extenuating proof, I come out
as a nice jackass.

It hurts to see the stupid mistakes one can do even after many years
spent working every day with databases :(

>Sounds like we need a spec...

you won't be surprised if I say that I am not dealing with an
astronomy problem.

I just transformed my dull schedule management problem into something
that could be fun.

Anyway, staying with the already known problem, we have the following
scenario:

STARS: Stars must have an ID - say Star_ID - (along with many more
fields).

Stars belong to a star/planet system. A star cannot belong to several
systems. Stars can belong to no system.

Several stars can belong to the same system.

PLANETS: Planets must have an ID - say Planet_ID. They will have
several more field, but this can be overlooked here.

SYSTEMS: a system is defined by a set of planets. Systems don't share
planets.

Arno Brinkman gave the solution I like most, and it is so simple!

Again, thanks to everybody

Duilio