Minggu, 19 April 2009

DATABASE AND ER-DIAGRAM

DATABASE AND ER-DIAGRAM
DATA BASE DEFINITION
· Stored nest of data in magnetic disk, optical disk or another secondary storage
· Inwrought collection from dates that mutual related from a enterprise (companies, government resort or private)
Manufacturing business –> Production planning data, recent production data, materials order data, etc
Hospital –> Patient data, doctor, nurse, etc.

DATABASE MANAGEMENT SYSTEM
DBMS is a system and the data base on the computer. This system is designed to be able to do a variety of data with some reference data are the same? DBMS is able to access various applications.
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



ATRIBUT/FIELD

· Is a character or characteristics from an entity that prepare detail explanation about that entity
· A relation also can has an attribute
· Attribute example:
o MAHASISWA: NIM, NAMA, ALAMAT
o MOBIL: NOMOR_PLAT, WARNA, JENIS, CC
TIPE-TIPE ATRIBUT
Single vs. multivalent
Single > can only be filled at most one value
Multivalent > 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, for example: age of the attributes generated from the date of birth.
Null Value Attribute
Attributes that have no value to a record
Mandatory Value Attribute
Attributes must have values
RECORD/TUPLE
· Is a data line in a relation
· Consist of a collection of attributes where that attributes mutual connected to give an information about an entity/relation completely
ENTITY/FILE
File is a collection of similar records and have the same elements, the same attributes but different data value.
ENTITY/FILE
· File is collection of a kind record and has same element , same attribute but has deferent data value.
· File type
· In application processing, file can classified as follows:
· Parent file
· Transaction file
· Report file
· History file
· Patron file
· Work file
DOMAIN
Domain is collection from values that permitted to stay in one or more attribute. Every attribute in a relational data base is defined as a domain.
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.
KINDS OF KEY
Super Key is one or more attribute from a table that can be used to identify entity/record from table uniquely (not all attributes can be super key)
Candidate Key is Super Key with minimal attribute. Candidate key can not full with attribute from other table so that Candidate Key is super key certainty but not yet certain on the contrary.
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
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 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 readings relationships.
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
Cardinalities
Type indicates the maximum number that can be borealis with entities on the other entity
RELATIONSHIP DEGREE
· Unary Relationship
Is a relationship model that happen between entities that come from it set entity.
· Binary Relationship
Is a relationship model that between 2 entity.
· Ternary Relationship
Is a relationship between instances from 3 types of entity unilaterally?
KARDINALITAS
There are 3 cardinalities 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 relationships 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 relationship with the first entity.
Many To Many:
If any incident occurs in an entity has many relationships with other entities in the incident.
EXEMPLARY KARDINALITAS




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 and entity





Reference:
1. ER Ngurah Agus Sanjaya. Slide Part 5 - DATABASE DAN ER-DIAGRAM.

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