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Boyce-Codd Normaalvorm
A relation scheme R is in BCNF if (and only if) for every non-trivial fd X Y F+ X is a superkey (for R).
A database scheme D = {R1,..., Rn} is in BCNF if (and only if) i {1,...,n}: Ri is in BCNF.
Let R = {A,B,C} and F = { A B, C B} and let us decompose R into by { R1 , R2 } where R1 {A,B} and R2 = {C,B}. Is this decomposition in BCNF? Is this the “best” decomposition in BCNF? (Can you find a better one?)
Notes:
De decompositie is in BCNF, maar ze is niet lossless join.
Laat ook met het algoritme een decompositie maken. (7.21)