DATABASE & ER-DIAGRAM

Definition of Database

Database is a set of data stored in the magnetic disc, optical disc, or other secondary storage. Integrated collection of related data from an enterprise (companies, goverment agecies or private).
- Manufacturing company : production planning data, 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.
- This application program used to access and maintain database.
- The main purpose DBMS (Database Management System) is to provide an environment that is efficient and easy to use, withdrawal and storage of data and information.

Bit, Byte, Field

- Bit is the smallest pieces of data that contains the value 0 or 1.
- Byte is a collection of bits-a bit like.
- Field is a set of byte-byte similar, in the database used the term attribute.

Attribute/Field

Attribute is the nature or characteristics of an entity that provides provide detail on these entities. A relationship can also have attributes.
Sample attributes :
- STUDENTS : NIM, NAME, ADDRESS
- CAR : PLAT_NUMBER, COLOR, TYPE, CC

Type Attribute

Single vs Multivalue
- Single typically can only be filled at most one value.
- Multivalue can be filled with more than one value with the same type of.
Atomic vs Composition
- Atomic can not be divided into the attributes of smaller.
- The composition is a combination of several attributes of a smaller.
Devired Attribute
Attribute value can be derived from other attribute values, Suppose that the age attribute of the date of birth.
Null Value Attribute
Attributes that have no value to a record
Mandatory Value Attribute
Attributes must have values

Record/Tuple

It is a line of data in a relationship, and consists of a set of attributes where the attribute is to inform each other entity/relationship fully.

Entity/File

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

File Type :
In processing applications, files can be categorized as follows:
- Master File
- Transaction File
- File Report
- File History
- File Protection
- File Work

Domain

Domain is the set of values that are allowed to reside in one or more attributes. Each attribute in a database relational is defined as a domain.

Element Key Data

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.

Species of Key

Superkey is one or more attributes of a table that can be used to identify entityty/record of the table are unique (not all attributes can be superkey).
Cadidate 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.

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 kardinalitas one to many (one to many) or many to many (many to many). Foreign key is usually always put on the table that lead to many.
External Key is a lexical attribute (or set of lexical attributes) that values are always identify an object instance.

ERD (Entity Relationship Diagram)

ERD (Entity Relationship Diagram) is a model of a network that uses word order is stored in the system of abstract.

Differences between the DFD (Data Flow Diagram) and ERD (Entitiy Relationship Diagram).
- DFD (Data Flow Diagram) is a model of network functions that will be implemented by the system.
- ERD (Entitiy Relationship Diagram) is a model that emphasizes the network data on the structure and relationship data.

Elements of the ERD (Entitiy Relationship Diagram)

- 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 the 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 readings relations.

- Relationship Degree
Is the number of entities participating in a relationship. Degree which is often used in the ERD (Entitiy Relationship Diagram).

- Attribute
Is the nature or characteristics of each entity and relationship.

- Cardinalitation
Tupel indicates the maximum number that can be relationships with entities on the other entity.

Degree of Relationship

- Unary Relationship is the relationship model between the entity originating from the same entity set.
- Binary Relationship is a relationship model between 2 entities.
- Ternary Relationship is a relationship between the instance of 3 types of entities are unilateral.

Cardinalitation

There are 3 kardinalitas 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 views. For an incident on the first entity can have any relationship with banyaj incident on the second entity, if the one incident in which two entities can only have one connection with incident on the first entity.
- Many to Many : If any incident occurs in an entity many have relationships with other entities in the event.