DATABASE AND ER-DIAGRAM

DATABASE AND ER-DIAGRAM

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). for example:

1. Company data > manufacturing production planning, actual production data, data ordering materials, etc.

2. 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

It is the nature or characteristics of an entity that provides provide detail on these entities. A relationship can also have attributes.

Examples for attributes:

STUDENTS: NIM, NAME, ADDRESS

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, 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

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 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 relasional 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.

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

3. Key is guaranteed unique

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 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 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

Kardinalitas

tupel indicates the maximum number that can be berelasi 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 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.

EXEMPLARY KARDINALITAS

NOTATION (E-R DIAGRAM)

Symbolic notation in the ER diagram is:

1. Rectangle represent the collective entity

2. Circle represent the attributes

3. Rhomb represent collective relationships

4. Line as the set of relations between the Association and the collective entity with entity attributes

Reference:

ER Ngurah Agus Sanjaya. Slide Part 5 - Database Dan Er-Diagram.