Definition of the database:

A set of data stored in the magnetic disk, optical disk or other secondary storage

Collection of integrated data-related data of an enterprise (company, government or private)

Manufacturing companies -> data production planning, actual production data, data ordering materials, etc.

Hospital -> patient data, doctor, nurse, etc.

Database Management System

- Collection / database combined with software applications that are based database

- Application programs are used to access and maintain databases

- The main purpose DBMS is to provide an environment that is efficient and easy to use, withdrawal and storage of data and information

Size in Database

Bit -> data is the smallest that contains the value 0 or 1

Bytes -> the set of bit-bit similar

Field -> byte-byte set of similar, in the database used the term attribute

Field / Attribute

It is the nature or characteristics of an entity that provides provide detail on these entities

A relationship can also have attributes

Example attributes:

STUDENTS: NIM, NAME, ADDRESS

CAR: NOMOR_PLAT, COLOR, TYPE, CC

Attribute Type :

- Single vs Multivalue

Single -> can only be filled at most one value

Multivalue -> can be filled with more than one value with the same type

- Atomic vs Composit

Atomic -> can not be divided into the attributes of smaller

Composition -> is a combination of several attributes of a smaller

- Derived attribute

attribute value can be derived from other attribute values, eg, -> age resulting from the date of birth attribute

- Null Value attribute

Attributes that have no value to a record

- Mandatory attribute Value

Attributes must have values

Record / Tuple

It is a line of data in a relationship

Consists of the set of attributes where the attribute-attribute-attribute is to inform each

other entity / relationship fully

Entity / File

File is a collection of similar records and have the same elements, the same attributes but different data value.

File Type

In processing applications, files can categorized as follows:

- Master File

- Transaction File

- File Report

- File History

- File Protection

- Job File

Domain

Domain is the set of values that are allowed to reside in one or more attributes.

Each attribute in a relational database is defined as a domain

Key Element

Key elements of record which is used to find these records at the time of access,

or can also be used to identify each entity / record / line.

Key Type :

- Superkey

is one or more attributes of a table that can be used to identify entity / record

of the table are unique (not all attributes can be superkey)

- Candidate Key

is a super key with minimal attributes. Candidate must not contain a key attribute

of the table so that the other candidate key is certain superkey but not necessarily vice versa.

- Primary Key

One of the key attributes of the candidate can be selected / specified a primary key with

the three following criteria:

1. Key is more natural to use as reference

2. Key is more simple

3. Key is guaranteed unique

- Alternate Key

is an attribute of the candidate key is not selected to be primary key.

- Foreign Key

is any attribute that points to the primary key in another table. Foreign key will be going on a relationship that has cardinality one to many (one to many) or many to many (many to many). Foreign key is usually always put on the table that point to many.

- External Key

is a lexical attribute (or set of lexical attributes) that values are always identify an object instance.

Entity Relationship Diagram (ERD)

ERD is a model of a network that uses word order is stored in the abstract system.

Differences between the DFD and ERD

DFD is a model of network functions that will be implemented by the system

ERD is a model that emphasizes the network data on the structure and relationship data

ERD’s Elements :

- Entity

In the ER Diagram Entity is described with the form of a rectangle. Rntity is something that exists in the real system and the abstract where the data stored or where there are data.

- Relationship

ER diagram on the relationship can be described with a lozenge. Relationship is a natural relationship that occurs between entities. In general, the name given to the verb base making it easier to do the reading their relationship.

- Relationship Degree

is the number of entities participating in a relationship. Degree which is often used in the ERD.

- Attribute

is the nature or characteristics of each entity and relationship

- Cardinality

tuple indicates the maximum number that can be related with entities on the other entity

Relationship Degree :

- Unary Relationship

model is the relationship between the entity originating from the same entity set.

- Binary Relationship

model is the relationship between 2 entities.

- Ternary Relationship

is a relationship between the instance of 3 types of entities are unilateral.

There are 3 cardinality relations, namely :

- One to One: Level one to one relationship with the one stated in the entity’s first event, only had one relationship with one incident in which the two entities and vice versa.

- One to Many or Many to One: Level one to many relationship is the same as the one to many depending on the direction from which the relationship .For an incident on the first entity can have any relationship with many incident on the second entity, if the one incident on the entity the second can only have one relationship with the incident on the first entity.

- Many To Many: if any incident occurs in an entity many have relationships with other entities in the incident.