DATABASE AND ER-DIAGRAM

DATABASE AND ER-DIAGRAM

DATABASE

1. DATABASE DEFINITION

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.

2. 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 part of smallest data which contains value of 0 or 1

- Byte is a set of similar bits

- Field is a set of similar bytes, in the database used the term attribute

- 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 of attributes:

- STUDENTS: NIM, NAME, ADDRESS

- CAR: CAR_NUMBER, COLOR, TYPE, CC

- TYPE-TYPE Attribute

- Single vs. multivalve

Single : can only be filled at most one value

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

- Atomic vs. composition

Atomic : cannot be divided into the attributes of smaller

Composition : combination of several attributes of a smaller

- Derived attribute

The attribute value can be derived from the value of other attributes, example : age can be derived resulting from the date of birth attributes

- Null Value attribute

Attributes that have no value to a record

- Mandatory attribute Value

Attributes must have values

3. RECORD / TUPLE

- It is a line of data in a relationship

- Consists of the set of attributes, the attributes relationship mutually to inform each other entity/full relationship

4. Entity / FILE

- File is a collection of similar records and have the same elements, the same attributes but different data value.

- File Type

In processing applications, files can categories, are:

- Master File

- Transaction Files

- File Reports

- File History

- File Protection

- File Work

5. 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

6. Element KEY DATA

- Key is element 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

7. 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 attribute of the another table so that the 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 unique

- Alternate Key is an attribute of the candidate key is not selected to be primary key.

- Foreign Key is any attribute those points to the primary key in another table. Foreign key will be going on a relationship that has cardinalities 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 identifying an object instance.

ERD (Entity Relationship Diagram)

1. ERD DEFINITION

- 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

2. 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 relationship

- 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

Indicates the maximum number of tupel that can be relation with entities on the other entity

- Unary Relationship

Is a model of the relationship between the entities originating from the same entity set

- Binary Relationship

Is a model of the relationship between 2 entities.

- Ternary Relationship

Is a relationship between the instances of 3 types of entities is unilateral.

3. Cardinality

There are 3 cardinalities relations, namely:

- One to One

Level one to one relationship with the one stated in the entities 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 much relationship is the same as the one to many depending on the direction from which look for the relationship. for an incident on the first entity can have any relationship with many incident on the second entity, if the one incident on 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 many have relationships with other entities in the incident.

4.

EXEMPLE OF CARDINALITY

5. Notation (E-R diagram)

Symbolic notation in the ER diagram is

1. Rectangle represents the collective entity

2. Circle represents the attributes

3. Belah Ketupat represents collective relationships

4. Link as the set of relationships between the collective relation with collective entity and the collective entity and with the attributes

Collective Entity

A key attribute of

Collective Relations

Link

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