August 2009
Intermediate to advanced
893 pages
26h 48m
English
Content preview from Database Systems: Concepts, Design and Applications
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10.4. Boyce-Codd Normal Form (BCNF)
To eliminate the problems and redundancy of 3NF, R.F. Boyce proposed a normal form known as Boyce-Codd normal form (BCNF). Relation R is said to be in BCNF if for every nontrivial FD: X → Y between attributes X and Y holds in R. That means:
X is super key of R.
X → Y is a trivial FD, that is, Y ⊂ X.
In other words, a relation must only have candidate keys as determinants. Thus, to find whether a relation is in BCNF or not, FDs within each relation is examined. If all non-key attributes depend upon only the complete key, the relation is in BCNF.
Any relation in BCNF is also in 3NF and consequently in 2NF. However, a relation in 3NF is not necessarily in BCNF. The BCNF is a simpler form of 3NF and eliminates ...