2. NORMALIZATION
Rajishma T
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3. Disclaimer: This presentation is prepared by trainees of
baabtra as a part of mentoring program. This is not official
document of baabtra –Mentoring Partner
Baabtra-Mentoring Partner is the mentoring division of baabte System Technologies Pvt .
Ltd

4. NORMALIZATION
 Normalization is the process of removing
potential anomalies from the database design.
These anomalies include:
– Insertion anomalies
– Update anomalies
– Deletion anomalies

5. INSERTION ANOMALIES
An insertion anomaly occurs when you can’t enter a
record in because some data is missing.
Consider a database with the rule that every
employee must be assigned to a project, but a newly
hired employee doesn’t have a project yet.
One solution is to create a dummy project, but this
puts bad data into your database and is not a good
idea.

6. UPDATE ANOMALIES
 Update anomalies occur when the same data
is stored in more than one place.
 This means whenever you have to make a
change to the data, you must do it in several
places.
 The more times you have to edit the same
data in multiple places, the more chances you
have of making a mistake, causing inconsistent
data.

7. DELETION ANOMALIES
causes other data to be lost Deletion anomalies
occur when deleting a record accidently .

8.  Normalization:
– The process of decomposing unsatisfactory "bad"
relations by breaking up their attributes into
smaller relations
 Normal form:
– Condition using keys and FDs of a relation to
certify whether a relation schema is in a particular
normal form

9. FIRST NORMAL FORM
 Only attribute values permitted are single atomic (or
indivisible) values
Techniques to achieve first normal form
– Remove attribute and place in separate relation
– Expand the key
– Use several atomic attributes

12. SECOND NORMAL FORM
 Second Normal Form removes what are called
“functional dependencies.”
 Functional dependencies are groups of columns that
depend on each other rather than on the key of the
table.

13.  Functional dependencies (FDs)
– Are used to specify formal measures of the
"goodness" of relational designs
– And keys are used to define normal forms for
relations
– Are constraints that are derived from the meaning
and interrelationships of the data attributes
 A set of attributes x functionally depends a set of
attributes Y if the value of X determines a unique
value for Y

14.  X -> Y holds if whenever two tuples have the
same valuefor X, they must have the same value
for Y
– For any two tuples t1 and t2 in any relation
instance r(R): If t1[X]=t2[X], then t1[Y]=t2[Y]
 X -> Y in R specifies a constraint on all relation
instances r(R)

15. SECOND NORMAL FORM
 Formal definition of 2NF is a table that is in
1NF and every non-primary-key column is fully
functional dependent on the primary key.
 Full functional dependency indicates that if A
and B are columns of a table, B is fully
dependent on A if B is functionally dependent
on A but not on any proper subset of A.

18. TRANSITIONAL DEPENDENCY
 Transitive functional dependency: a FD X -> Z that
can be derived from two FDs X -> Y and Y -> Z
 For example, consider a table with A, B, and C.
If B is functional dependent on A and C is
functional dependent on B , then C is
transitively dependent on A via B (provided that
A is not functionally dependent on B or C).
 If a transitive dependency exists on the
primary key, the table is not in 3NF.
`

21. BCNF
A relation R is in Boyce/Codd N/F (BCNF) if and only if
every determinant is a candidate key. Here, determinant
is a simple attribute or composite attribute on which
some other attributes is fully functionally dependent.
Each normal form is strictly stronger than the previous
one
Every 2NF relation is in 1NF
Every 3NF relation is in 2NF
Every BCNF relation is in 3NF
 There exist relations that are in 3NF but not in BCNF
 The goal is to have each relation in BCNF (or 3NF)

22. campus course class time Room/bldng
east English 101 1 8:00-9:00 212 AYE
east English 101
2 10:00-11:00 305 RFK
West
English 101 3 8:00-9:00
102 PPR

23. • no two buildings on any of the university campuses
have the same name, thus ROOM/BLDG-----
>CAMPUS. As the determinant is not a candidate key
this table is not in bcnf.
• R1(course, class, room/bldg, time)
•
course class time Room/bldng
English 101 1 8:00-9:00 212 AYE
English 101 2 10:00-11:00 305RFK
English 101 3 8:00-9:00 102PPR

24. • R2(room/bldg, campus)
campus Room/bldng
east 212 AYE
east 305 RFK
west 102 PPR

25. Identify all candidate keys in the relation.
Identify all functional dependencies in the
relation.
If functional dependencies exists in the relation
where their determinants are not candidate keys for
the relation, remove the functional dependencies by
placing them in a new relation along with a copy of
their determinant.

26. FOURTH NORMAL FORM
4NF: A relation that is in Boyce-Codd Normal
Form and contains no MVDs.
BCNF to 4NF involves the removal of the MVD
from the relation by placing the attribute(s) in a
new relation along with a copy of the
determinant

27. MVD multi-valued dependency
• Represents a dependency between attributes
(for example, A, B, and C) in a relation, such that
for each value of A there is a set of values for B,
and a set of values for C. However, the set of
values for B and C are independent of each
other

28. 50
Normalization
BCNF to 4NF Relations

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