Curs Normalization

7/23/2019 Curs Normalization

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NORMALIZATION

LAURENTIU FRATILA, PH.D.



Normalization is defined as a conceptual modeling technique that aimsprocessing attributes in entities in order to eliminate logical and physicalanomalies .

This will improve the conceptual modeling phase of data, resulting in improveddatabase structure and thus eliminate some malfunctions, such as redundancy,anomalies that may occur in the process of updating the database (anomaliesof adding, modifying , delete attributes).

During normalization, we use the term relationship for conceptual entity, too.The relationship is a lot of domains plus a lot of name-value pairs, one pair foreach domain and value are into the domain of the name.



Anomalies in adding process: do not allow the introduction of newinformation in a table because other useful information are not known to inserta new tuple in the table.

Code_client

Name_client

Type_dep

Date_dep

Amount

Interest_rate

12371 Anghel D-1-M 02/03/13 1000 0.02

12456

Tudor

D-3-M

05/04/13

700

0.03

15542 Vasile D-6-M 07/06/04 1500 0.04

17823

Zainea

D-12-M

05/07/13

3000

0.06



Anomalies in changing process: can not be changed values of attributes foran entity without doing changes in all entities in which it appears that attribute.

Series_ID_cl

No_ID_cl

Name_cl

Type_dep

Date_dep

Amount

Interest_ rate

AC

153268

Anghel

D-1-M

02/03/13

1000

0.02

AZ 542689 Tudor D-3-M 05/04/13 700 0.03

ST 159834 Vasile D-6-M 07/06/13 1500 0.04

AC

153268

Anghel

D-6-M

02/05/13

1000

0.04

SZ

483267

Zainea

D-12-M

05/07/13

3000

0.06



Anomalies in deleting process: deleting a tuple from an entity can generatedeleting useful information existing in that tuple.

Normalization is based on the theory of normal forms. The first three normalforms were defined by Codd, and the fourth and fifth normal forms weredefined by Fagin.

Code_client

Name_client

Type_dep

Date_dep

Amount

Interest_rate

12371 Anghel D-1-M 02/03/13 1000 0.02

12456

Tudor

D-3-M

05/04/13

700

0.03

15542 Vasile D-6-M 07/06/04 1500 0.04

17823

Zainea

D-12-M

05/07/13

3000

0.06



The First Normal Form (NF1) A relationship is in first normal form (NF1) if all attributes contain elementary

values, values that can not be decomposed. In the same time, each tuple does

not have to be repeated groups.

Steps to bring a relationship to NF1 are: 1. Decomposition the composed attributes in elementary attributes and replace

them in the relationship 2. Creating a new relationship for repetitive attributes

3. Set up new relationship identifier that will be formed from the initialrelationship identifier, plus a minimum number of attributes for defining amultiple identifier.



Code_cl Name_cl First_name_cl Address_cl Type_dep No_dep

123715

Anghel

Marin Cluj, str. Turda,

nr. 8

D-1-M

345

124568 Tudor Dragos Iasi, str.Unirii, nr. 2

D-6-M 690

Name_dep

Date_dep

Amount Interest_

rate

Code_employee

Name_ employee

1 Month Deposit

06/04/13

200

0.02

123

Ion Maria

6 Months Deposit

05/06/13

500

0.04

125

Radu Victor



The Second Normal Form (NF2) A relationship is in normal form 2 (NF2) if it comply with NF1 and every non-key

attribute is fully dependent on the primary key.

The non-key attribute is any attribute of the relationship, different from theprimary key

Steps to bring a relationship from NF1 to NF2 are: Determination of partial dependencies between non-key attributes and key

attributes.

Creating new relationships that will include initial entity identifier, the attributesthat were determined in the previous step and all the attributes that aredetermined.

Set up new relationships identifiers, that will be formed from the initialrelationship identifier and the attributes/group of attributes that are directlydependent by the identifier, set up in step 1.



Code_cl

Type_dep

No_dep

Name_dep

Date_dep

Amount

123715

D-1-L

345

1 Month Deposit

06/04/13

200

123715 D-6-L 690 6 Months Deposit 05/06/13 500

123715

D-3-L

723 3 Months

Deposit

07/06/13

300

Interes_rate Code_employee Name_employee

0.02

123

Ion Maria

0.04 125 Radu Victor

0.03 456 Ion Maria



The Third Normal Form (NF3) A relationship is in normal form 3 (NF3) if it comply with NF2 and contains no

transitive dependencies of non-key attributes in relation to the primary key.

Steps to bring a relationship from NF2 to NF3 are: Determination of the attributes that are in a transitive dependency to the

primary key Creating of new relationships, determined by the previously set attributes and

the attributes that are determined plus initial entity identifier

Set up new relationships identifier, that will consist of the original relationshipidentifier and the attribute/group of attributes directly dependent by theidentifier set in step 1



Code_cl Type_

dep

No_dep

Name_dep Date_

dep

Amount Interest_

rate

Code_employee

123715

D-1-L

345

1 Month Deposit

06/04/13

200

0.02

123

123715 D-6-L 690 6 MonthsDeposit

05/06/13

500 0.04 125



Boyce-Codd Normal Form (BCNF) A relationship is in Boyce-Codd Normal Form (BCNF) if and only if every

determinant is a candidate-key.

To develop normal forms, Boyce and Codd introduced the concept ofdeterminant.

A determinant is any attribute, simple or compound, through any other attributeis fully functionally dependent.



The Fourth Normal Form (NF4) A relationship is in the normal form 4 (NF4) if it is in NFBC and does not contain

multiple dependencies.

Code_employee Function Departament

…..

456 credit officer credit

457

director

credit

457

director

credit 459 economist marketing

…



In practice entities are transformed in compliance with the NF1-NF4.

Sometimes there are cases where it will make a de-normalization of the entities,

which lead to redundancies among the attributes of the model, but this,although not recommended, has the effect of certain reports easier getting fromthe bank management at some time.

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