The document discusses Boyce-Codd normal form (BCNF), which is a normal form used in database normalization that is stricter than third normal form (3NF). A table is in BCNF if every functional dependency has a left-hand side that is a super key of the table. Three examples are provided to illustrate the concept: an example of a relation in BCNF, an example of a relation not in BCNF because it violates 2NF, and an example of a relation in BCNF because the left-hand side of each functional dependency is a candidate key.

1. Arvin Bera
CST, KPC
Normalization

2. Learning OutCome
 BCNF
 Definition
 Comparisons with others
 Examples

3. BCNF(Boyce–Codd normal form)
Boyce–Codd normal form (or BCNF or 3.5NF) is
a normal form used in database normalization. It
is a slightly stronger version of the third normal
form (3NF).
1. BCNF is the advance version of 3NF. It is
stricter than 3NF.
2. A table is in BCNF if every functional
dependency X → Y, X is the super key of the
table.
3. For BCNF, the table should be in 3NF, and for
every FD, LHS is super key.

4. All Normal Form

5. Example-1
 Consider relation R(A, B, C)
 A -> BC, B -> A
 A and B both are super keys so above relation is
in BCNF.

6. Example-2
 Consider relation R(A, B, C,D,E)
 {AB->C,C->D,D->E,E->A}
 We have to find out the candidate keys
 (AB)+->ABCDE
 (BC)+->BCDEA
 (BD)+->BDEAC
 (BE)+->BEACD
 But C->D,D->E,E->A implies
 Partial key->partial key
 So the R is not in 2NF so it will not be in BCNF

7. Example-3
 Consider relation R(A, B, C)
 {A->BC,B->AC,C->AB}
 So A,B,C all are candidate keys.
 So left hand side of the F.D is candidate key
 So the R is in BCNF