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Boyce-Codd Normal Form (BCNF)

A stricter version of 3NF in which every determinant (left side of a functional dependency) is a candidate key.

Definition

BCNF handles anomalies that 3NF can miss when a table has overlapping composite candidate keys. Every BCNF table is in 3NF, but not every 3NF table is in BCNF. Decomposing to BCNF can sometimes lose dependency preservation.

Exam tip

If a non-candidate-key attribute determines part of a key, the table is in 3NF but not BCNF.

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