NORMALIZATION

Process Design Database

- Gether user need/business
- Develop a needs-based ER Model user/business
- Convert E-R model to the set of relations (tables)
- Normalization to remove the anomaly relations
- Implemented to create a database with a table for each relationship that is normalization

Database normalization

Normalization process is the establishment of the database structure so that most of the ambiguity can be removed. Normalization stage, starting from the most mild (1NF) to most stringent (5NF). Usually only up to the level of 3NF or BCNF because already sufficient to generate the table-table good quality.

Why do normalization?
- Optimizing table structures
- Increase speed
- The income data is the same
- More efficient in the use of storage media
- Reduce redundancy
- Avoid anomalies (insertion anomalies, deletion anomalies, update anomalies)
- Improved data integrity

A table saying good (efficient) or if the normal 3 to meet the following criteria :
- If there is decomposition (decomposition) table, it must be guaranteed safe dekomposisinya (Lossless-Join Decomposition). That is, after the table is described / didekomposisi a new table-table, the table-table can generate a new table with the same exact.
- Maintain dependence on the functional changes in data (Dependency preservation)
- Does not violate Boyce-Code Normal Form (BCNF)

If the three criteria (BCNF) can not be met, then at least the table does not violate the Normal Form of the third stage (3rd Normal Form / 3NF)

Functional Dependency

Functional Dependency describes a relationship attributes in relation. An attribute said functionally dependant on the other, if we use the value attribute to determine the value of other attributes. Symbol that is used to represent the functional dependency that is readable in determining functional.

Notation : A --> B
A and B are attributes of a table. A means of determining the functional B or B depends on A, if and only if there are 2 rows of data with the same value of A, then B is also the same value.

Notation : A --> B or A x --> B
It is the opposite of the previous notation.

FUNCTIONAL DEPENDENCY (FD)



Functional Dependency
NRP --> Nama
Mata_Kuliah, NRP --> Nilai

Non Functional Dependency
Mata_Kuliah --> NRP
NRP --> Nilai

Functional Dependency of the table value
- NRP --> Nama
Karena untuk setiap nilai Nrp yang sama, maka nilai Nama juga sama.
- {Mata_kuliah, NRP} --> Nilai
Because the value of attributes depending on the NRP and Mata_kuliah together. In another sense Mata_kuliah for the NRP and the same, they also rated the same, because Mata_kuliah and the NRP is a key (a unique).
- Mata_kuliah --> NRP
- NRP --> Nilai

FIRST NORMAL FORM – 1NF

A table on the form said to be normal if I did not reside in the unnormalized form of a table, where there is a kind of field multiplication and field that allows a null (empty).

Not allowed the:
- Many attributes of value (Multivalued attributes).
- Attributes composite or a combination of both.

So the price should be the domain attribute price atomic

Ex Student Data as follows:

Or:

The table above does not meet the requirements 1NF

Example :

Dekomposisi menjadi :
- Table Student

- Table Hobby


SECOND NORMAL FORM

Normal form 2NF met in a table if it meets the form of 1NF, and all the attributes than the primary key, have a full Functional Dependency on primary key. A table does not meet 2NF, if there are attributes that ketergantungannya (Functional Dependency) are only partial (only depending on the part of the primary key). If there are attributes that have no dependence on the primary key, then the attributes must be moved or removed. Y is full if it is said to delete an attribute A from X means that Y is no longer dependent functional --> Functional dependency X. Y said if deleting a partial attribute A from X means that Y is functionally dependent --> Functional dependency X. Relation scheme R in the form 2NF if every non-primary key attribute A element R depends on the full primary key fungsioanl R.

Example :

The following table meet 1NF, including but not 2NF


Does not meet 2NF, because (NIM, KodeMk) is regarded as the primary key:
{NIM, KodeMk} --> NamaMhs
{NIM, KodeMk} --> Alamat
{NIM, KodeMk} --> Matakuliah
{NIM, KodeMk} --> Sks
{NIM, KodeMk} --> NilaiHuruf

Table needs to be some table decomposition eligible 2NF

Functional dependency:
- {NIM, KodeMk} --> NilaiHuruf (fd1)
- NIM --> {NamaMhs, Alamat} (fd2)
- KodeMk --> {Matakuliah, Sks} (fd3)

So:
- fd1 (NIM, KodeMk, NilaiHuruf) --> Tabel Nilai
- fd2 (NIM, NamaMhs, Alamat) --> Tabel Mahasiswa
- fd3 (KodeMk, Matakuliah, Sks) --> Tabel MataKuliah

THIRD NORMAL FORM – 3NF

Normal form 3NF fulfilled if the form meets 2NF, and if there are no non-primary key attribute that has a dependence on non-primary key attributes of the other (transitive dependencies).

Example :

Table following students eligible 2NF, 3NF, but does not meet :


Because there are non-primary key attribute (ie, City and Provincial), which has a dependence on non-primary key attributes of the other (is KodePos):
KodePos --> {Kota, Provinsi}

So that the table should be decomposition :
Students (NIM, NamaMhs, Jalan, KodePos)
- KodePos (KodePos, Provinsi, Kota)

Boyce-Codd Normal Form (BNCF)

Boyce-Codd Normal Form constraint has a stronger form of the Normal third. To be BNCF, relations must be in the form of Normal Kesatu and forced each of the attributes depends on the function in the super key attributes.

In the example below there is a relationship seminar, is the Primary Key NPM + Seminar.
Students may take one or two seminars. Each seminar requires 2 each of the students and led by one of the 2 seminar. Each leader can only take one seminar course. NPM in this example indicates a seminar and teacher.




Relations Seminar is a form of Third Normal, but not BCNF
Seminar Code because the function depends on the Pembimbing, if any Pembimbing can only teach a seminar. Seminar depend on one key attribute is not as super disayaratakan by BCNF.

Normal Form Of The Fourth And Fifth

Relations in the fourth normal form (NF 4) if the relation in BCNF and dependency tdak contain many values. To remove the dependency of many values from a relation, we divide the relationship into two new relations. Each relation contains two attributes that have a lot of relationship value. Relations in fifth normal form (5NF) deal with the property called the join without any loss of information (lossless join). Fifth normal form (also called the 5 NF PJNF (projection join normal form). The case is very rare and appear difficult to detect in practice.