DATABASE AND ER-DIAGRAM

DATABASE AND ER-DIAGRAM

Database is a set of data stored in the magnetic disk, optical disk or other secondary storage. User and administrator can inserting, deleting and updating data. The different between user and administrator is in the accessing right. Collection of integrated data-related data of an enterprise (company, government or private). for example:
1. Company data : production planning, accounting data, company organizing, actual production data, data ordering materials, staff data etc.
2. Government : amount of resident data, government planning, nation income data, etc.
3. Private : private document, foto, etc.
DATABASE MANAGEMENT SYSTEM
. DBMS is a collection of databases or a combination of software-based database applications. DBMS is a software designed to assist in the maintenance and utility data collection in large numbers. 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
1. Bit is the smallest pieces of data that contains the value 0 or 1
2. Byte is a set of bit-bit similar
3. Field is a set of byte-byte similar, in the database used the term attribute
ATTRIBUT/FIELD
Attribute is the nature or characteristics of an entity that provides provide detail on these entities. A relationship can also have attributes. Example attributes:
1. STUDENTS: NIM, NAME, ADDRESS
2. CAR: NOMOR_PLAT, COLOR, TYPE, CC
TIPE-TIPE ATRIBUT
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’t 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 that have relationship, for example: age of the attributes generated from the date of birth, zodiac of attributes generated from the date of birth, etc.

Null Value Attribute
Attributes that have no value to a record or the attributes have no generate. For example phone number in x’self data.
Mandatory Value Attribute
Attributes must have values

RECORD/TUPLE
Record is a data line in a relationship. Record consists of a set of attributes where the attribute is an attribute-related entity or to inform the full relationship.
ENTITAS/FILE
File is a collection of similar records and have the same elements, the same attributes but different data value.
File Type
File is a collection of notes and similar elements have the same, the same attributes but different data values. In the process of application, the file can be in the category with some of the following types
1. Master File
2. Transaction File
3. File Report
4. File History
5. File Protection
6. 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
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 DATA 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.
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 attribute from candidate key can be choose/determined to be primary key with three criterias as follows:
1. That key more natural to be used as reference
2. That key is simpler
3. That key well guaranted the uniqueness
• Alternate key is attribute from candidate key that not chosen be primary key.
• Foreign key is just any attribute that indicate to primary key in other table. Foreign key will happen at one particular relation that has cardinality one to many or many to many. Foreign key usually always put in table that aim to many.
• External key is a lexical attribute (or collection lexical attribute) that the values always identify one object instance.

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 or 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 network model that use wording that kept in system according to abstract.
• Difference between DFD and ERD :
o DFD is a function network model that would carried out by the system
o ERD is a data network model that emphasized in structure and relationship data

ELEMENTS OF ERD
• Entity
In ER Diagram entity described with long square form. Entity is something that there in real system also or abstract where does stored data or where does found data.
• Relationship
in ER Diagram relationship can be described with a trapezoid. relationship is a natural connection that happen between entity. in general given name with verb base so that make easy to do the relation reading.
• Relationship degree
Is a total entity that participate in one relationship. degree often worn in ERD.
• Attribute
Is a character or characteristics from every entity and also relationship
• Cardinality
Show optimum tupel that can be related with entity in another entity

RELATIONSHIP DEGREE
• Unary Relationship
Is a relationship model that happen between entity that come from same set entity.
• Binary Relationship
Is a relationship model that between 2 entity.
• Ternary Relationship
Is a relationship between instance from 3 types of entity unilaterally.

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 is viewed. For one incident in the first entity can have many relationships with the incident on the second entity, if the one incident in which two entities can have only one incident hubugan with the first entity.
Many To Many:
if any incident occurs in an entity has many relationships with other entities in the incident.

NOTATION ER-DIAGRAM
Symbolic notation in diagram er is :
1. Long square that declares collection of entity
2. Circle that declares attribute
3. Trapezoid declares relation collection
4. Line as liaison between relation collection with entity collection