DATA BASE AND ER- Diagram

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)

A companies manufacturing production planning data, actual production data, data ordering materials, etc.

A 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 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, with drawal and storage of data and information

BIT, BYTE, Field

A part is a bit of data which contains the smallest value of 0 or 1

Byte a-bit set of bit similar

Field a-byte set of bytes is similar, in the data base used the term attribute

NIM NAME ADDRESS

9455500001 Abdullah objects RAYA NO 4

9455500002 Aminah CILEDUG NO 4

9455500003 Budiman Halimun NO 7

Attribute / 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. multivalue Single a can only be filled at most one value a

Multivalue can be filled with more than one value with the same type of

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

Derived attribute attribute value can be derived from the value of other attributes, eg age a attributes resulting from the date of birth

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 values.

File Type

In processing applications, files can follows occupy meaning:

- Master File

- Transaction Files

- File Reports

- File History

- File Protection

- File Work

DOMAIN

- Domain is a set of values that are allowed to reside in one or more attributes. Each attribute in a database relasional 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

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 uniqueness.

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 (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. ER 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 relations.

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 cardinalitationstuple indicates the maximum number that can be relations 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 two entities.

Ternary Relationship is a relationship between the instance of three types of entities are unilateral

CardinalitationThere

are three cardinalitation 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 eyes.For an incident on the first entity can have any relationship with incident many on the second entity, if the one incident on the the second entity can only have one relationship with the incident on the first entity. Many To Many: if any incident occurs in an entity have many relationships with other entities in the event

EXEMPLARY KARDINALITAS

Notation (E-R diagram)
symbolic notation in the ER diagram is

1. rectangle represent the collective entity

2. circles represent attributes

3. rhomb stated set of relationships

4. line as a link between the collective set of relationships with the entity and the collective entity with attributed.