DATABASE & ER-DIAGRAM

DATABASE & ER-DIAGRAM

Definition

§ The database is 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 instance or private).
Company a manufacturing : production planning data, actual production data, data ordering materials, etc.
Hospital : patient data, doctor, nurse, etc.

DBMS

§ System that is specifically created to make it easier to manage users in the database. The main purpose DBMS is to provide an environment that is efficient and easy to use, withdrawal and storage of data and information.

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

Bit, Byte, Field

§ Bit : Data bit is the part that contains the smallest value of 0 or 1.

§ Byte : Byte is a set of bit-bit similar

§ Field : Field is a set of byte-byte similar, in the database used the term attribute

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 of

§ Atomic Vs Composition
Atomic: can not be divided into the attributes of smaller
Composition: is a combination of several attributes of a smaller

§ Derived attribute
Attributes are derived attribute whose value can be derived from the value of other attributes, age attributes resulting from the date of birth

§ Null Value attribute
Attributes that have no value to a record

§ Mandatory attribute Value
Attribute should have a value

RECORD/TUPLE

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

§ In processing applications, files can categorized as follows:
- Master File
- Transaction Files
- File Reports
- 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 relasional is defined as a domain

DATA ELEMENT KEY

§ 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 TYPES

• 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)
• 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 is one of the key attributes of the candidate can be selected / specified a primary key
• 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 point to many.
• External Key is a lexical attribute (or set of lexical attributes) that values are always identify an object instance.

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 ELEMENT

§ Entity
In the ER Diagram Entity is describe with the form of a rectangle. Entity 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 read the relation.

§ Relationship Degree
is the number of entities participating in a relationship. Degree which is often use in the ERD.

§ Attribute
Attribute is the nature or characteristics of each entity and relationship.

§ Kardinalitas
Tupel indicates the maximum number that can be relation 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.

KARDINALITAS

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 dilihat.Untuk 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 hubugan with the incident on the first entity.
• Many To Many: if any incident occurs in an entity most have relationships with other entities in the incident.

EXAMPLES KARDINALITAS

NOTATION (ERD)

§ Symbolic notation in the ER diagram is :
1. Rectangle represent the collective entity
2. Circle represent the attributes
3. Rhomb express collective relationships
4. Line as the set of relationships between the collective relation whit the collective entity and collective entity with attribute.

(ENTITY COLLECTIVE, ATTRIBUTE A AS KEY, RELATION COLLECTIVE, AND LINK)