DATABASE AND ER-DIAGRAM

DEFINITION Database

• 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 production planning, actual production data, data ordering materials, etc.
• Company data
  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

BIT, BYTE, FIELD

• bit is the smallest pieces of data that contains the value 0 or 1
• Byte – set of bit-bit similar
• Field – set of byte-byte similar, in the database used the term attribute

ATRIBUT/FIELD

• 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

TYPE-TYPE Attribute

• Single vs. multi value
  can be filled only at most one value
  • Single
    can be filled with more than one value with the same type of
  • Multi value

• Atomic vs. composition
  can not be divided into the attributes of smaller
  • Atomic can not be divided into a smaller attribute
  • Composition is a combination of several attributes of a smaller

TYPE-TYPE Attribute (2)

• Derived attribute
  • attributes resulting from the date of birthàattribute value can be derived from the value of other attributes, eg age
• 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 in its value.
• File Type
  In processing applications, files can be 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 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

• Super key 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 super key)
• 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 super key 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 its uniqueness

SPECIES OF KEY (2)

• Alternate Key is an attribute of the candidate key is not selected to be primary key.
• Foreign Key is any attribute that point to the primary key in another table. Foreign key will be going on a relationship that has cardinalities 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 (Entity Relationship Diagram)

• 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

Elements of the ERD

• Entity
  In the ER Diagram Entity is described 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 the reading that relation
• 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
  tupel indicates the maximum number that can be related with entities on the other entity

Degree of relationship

• 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.

CARDINALITY

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 to be seen. 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 relationships 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.

Notation (E-R diagram)

Symbolic notation in the ER diagram is

• 1. Rectangle represent the collective entity
  2. Circle represent the attributes
  3. Rhomb part explains collective relationships
  4. Line as the set of relationships between the entity and the collective entity with that Set of attributes