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Beer example 2
b(b,k(L V) Ç S))
L V gives drinkers with beers they like and bars they visit.
We project on b,k so these are beers and bars such that someone visits the bar who likes the beer.
We intersect with S, hence we have beer-bar combinations such that someone who likes the beer visits the bar and the bar also serves the beer. (In fact this intersection means the same as the join!)
Conclusion is just the beer: List the beers that are served in a bar where some visitor(s) like that beer.
Notes:
Deze query komt van Rolph de Ruiter (fout antwoord voor bier vraag n).