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In-Depth Information
BCNF
3NF
normalization
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Fig. 9.7 Normalizationof BCNF
For example: Relation CTT ( Course , Teacher , Text ) consists of MVD Course 
Teacher, and MVD Course  Text before normalization.
After normalization, Relation CT ( Course , Teacher ) with FD: Course,
Teacher 0, and Relation CX ( Course , Text ) with Course, Text 0, and they are
without MVD. Therefore, they are in 4NF. The normalized relations can be denor-
malized by joining them together to recover the original BCNF relation (Fig. 9.8 ).
There are anomalies of BNCF in insert. For example, to add the information that
the physics course uses a new text called Advanced Mechanism, it is necessary to
create three new tuples, one for each of the three teachers.
Similarly, for two relations CT (Course, Teacher) and CX (Course, Text),
they can be reconstructed into relation CTT (Course, Teacher, Text) with MVD
Course  Teacher|Text in 2-decomposibility.
A relation is in fifth normal form (5NF) if there is no join dependency (JD)
within the relation as shown below:
JD: Project Attributes
Project Attributes Relation
(Attributes,… Attributes)
Normalizedinto
Relation with JD 5NF Relations(without JD)
Eliminate JD
A join dependency means that if there binary relationships occur in three attributes
a, b, c, then there is a join dependency in these three attributes.
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