I think you have the basis of an interesting model there Jeroen, but I'm a little concerned by the language you are using there. groups don't have a championship, rahter a championship is comprised of several groups. ie the championship is the parent entity , the groups are the tables that comprise the various qualification stages out of which the eventual winner appears
the relationship should reflect the order of precedence
lets say you are modelling UEFA or FIFA
they hold championships, in which registered national sides compete for various events
so an organising authority has member events (so the precedence is an organising authority entity, that is referred to in the events entity)
a nation is affiliated to one or more organising authorities (eg FIFA, UEFA)
a championship os made up of various matches between specific teams (nations).
so there should be a row in, say, your championship table which is referred to from other rows identfying the countries playing in that championship.
however depending on what you are trying to model ther is another layer of complexity. is your model tryng to refelct a single championship say Euro 2010? ir is it trying to reflect every Euro Championship, and optionally every FIFA world cup....
the reason why I ask is that this changes the model significantly, because you have to account for not just each team each match, each table but qualify that for each and every year.
I'd rather be riding on the Tiger 800 or the Norton