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In-Depth Information
4NF
5NF
S#
P#
J#
J#
S#
P#
J#
S#
P#
Normalization
S1
P1
J2
J2
S1
P1
J2
S1
P1
SP
S1
P2
J1
J1
S1
P2
J1
S1
P2
S2
P1
J1
J1
S2
P1
J1
S2
P1
S1
P1
J1
Denormalization
Join over P#
JS
PJ
Relation SPJ
S# P# J#
S1 P1 J2
S1 P1 J1
S1 P2 J1
S2 P1 J2
S2 P1 J1
Join over (J#, S#)
•
SPJ is the join of all of its three projections,
not of any two!
Spurious
7/25/2014
4NF
5NF
3-decomposability
S#
S#
S
S
n
n
n
n
Normalization
R2
R1
:
:
:
:
Denormalization
R
m
m
m
m
P#
J#
R3
J
P
J
P#
J#
P
m : n
Fig. 9.9
Normalization of fifth normal form (5NF)
Since they do not have JD, therefore they are in 5NF. The normalized relations
can be denormalized by joining them together to recover the original 4NF relation
(Fig.
9.9
).
Given a relation SPJ in 4NF, there are abnormalies in insert. If insert (S1, P1, J2),
(S1, P2, J1), and (S2, P1, J1), then (S1, P1, J1) must also be inserted. On the other
hand, if one of (S1, P1, J2), (S1, P2, J1), and (S2, P1, J1) is deleted, then (S1, P1,
J1) must also be deleted.
For n-ary relationship, a ternary relationship of three decomposability in this
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