DATABASE AND ER-DIAGRAM

DATABASE AND ER-DIAGRAM

DATABASE DEFINITIONS
Database is a group of on file data in disk magnetic, disk optical or is depository of other sekunder. Inwrought collection of data-data which each other is interconnected the than a enterprise (company, governmental institution or private sector). Example:
- Manufacturing business (production planning data, data produce aktual, data ordering of material, etc)
- Hospital (patient data, doctor, nurse, etc)

DATABASE MANAGEMENT SYSTEM
Database management system represent database aliance or corps with software of application being based on database. This application programs is used to access and look after database. Especial target of DBMS is to provide a efficient and easy environment for the usage of, to withdrawal and is depository of information and data.

BIT, BYTE, FIELD
- Bit representing part of containing smallest data of value 0 or 1.
- Byte representing corps of beets which of a kind.
- Field representing a group of byte-byte which of a kind, in data bases used by attribute term.

FIELD OR ATTRIBUTE
Field or attribute representing the nature of or characteristic from entitas providing to provide clarification of detail about entitas. A relationship also can have attribute. Example: STUDENT (NIM,NAMA,ADDRESS),CAR(PLAT_NUMBER,COLOUR,TYPE)

TYPE-TYPE ATTRIBUTE
- Single vs Multivalue:
- Single, only can fill at most one value
- Multivalue, can fill with interest from one value with same type

- Atomic vs Composition:
- Atomic, indiscrete into smaller attribute
- Composition, representing aliance from some smaller attribute

- Derived Attribute:
- Attribute which its value can be which yielded from other attribute value, for example age which yielded from attribute birthday
- Null Value Attribute:
- Attribute which don’t have value to a record

- Mandatory Value Attribute:
- Attribute which must have value

RECORD/TUPLE
Record or Tuple representing data line in a relationship. Consist of attributes corps where attributes of interaction to inform entitas or relationship completely.

ENTITAS/FILE
File represent corps of record which of a kind and have is same element, is same attribute but different each other its data.
- Type File
In application process, file can be categorized as follows:
- File Mains
- File Transaction
- File Report
- File History
- File Protector
- File Job

DOMAIN
Domain represent corps of values enabled to stay in one or more attribute. Every attribute in data bases of relasional defined by as a domain.

KEY DATA ELEMENT
Key is element of record weared to find the the record when accessing or can is also used to identify every entity/record/line.

TYPES OF KEY
- Superkey represent one or more attribute from tables of able to be used to identify entity/ record of tables uniquely (not all attribute can become superkey)
- Cadidate Key is super of key with minimum attribute. Key Candidate may not contain attribute of other tables so that key candidate beyond question superkey but not yet of course on the contrary.
- Primary Key
One of the attribute of key candidate can be selected/ to be determined to become key primary with three the following criterion:
- The Key more natural to be used as reference
- The Key more simple
- The Key well guaranted it

- Alternate Key is attribute of key candidate which is not chosen become key primary
- Foreign Key represent any attribute subjecting to key primary at other tables. Key Foreign will happened at one particular relationship owning many to one cardinality ( one to many) or many to many ( many to many). Key Foreign usually is always put down by at tables of which is flange to many
- External of Key represent attribute lexical ( or gathering of lexical attribute) which is it values always identify one object of instance

ERD (ENTITY RELATIONSHIP DIAGRAM)
ERD is network model using wording which is kept in system abstractionly.
Difference between DFD and ERD:
- DFD represent a[n function network model to be executed by system
- ERD represent data network model emphasizing at and structure of relationship data

ELEMENTS OF ERD
- Entity
At ER Diagram of Entity depicted with square form of length. Entity is something that there is in real system and also abstraction where on file data or where there are data
- Relationship
At ER Diagram of relationship can be depicted with a is lozenged. Relationship is natural relation that happened between entitas. In general called with elementary verb so that facilitate to do read of its relationship
- Relationship Degree
Relationship Degree is the amount of entitas participating in one relationship. Degree of which is often weared in ERD
- Attribute
Attribute is the nature of or characteristic of each and also entitas of relationship
- Cardinality
Showing optimum of tuple able to relationship with entitas at other entitas

DEGREE OF RELATIONSHIP
- Unary Relationship
Unary Relationship is model of relationship that happened between entity coming from entity set same.
- Binary Relationship
Binary Relationship is model of relationship that happened between 2 entitas.
- Ternary Relationship
Ternary Relationship representing relationship between instance from 3 type of entitas unilaterally.

CARDINALITY
There are 3 relationship cardinality that is:
- One to One: Level relation one to one expressed with one occurence at first entitas, only having one relation with one occurence at second entitas conversely.
- One to Many or Many to One: Level relation one to many is equal to many to one depended from which direction of the relation seen. To one occurence at first entitas can have many relation with occurence at second entitas, if on the contrary one occurence at second entitas can only have relation with one occurence at first entitas.
- Many To Many: Happened if every occurence at a entitas have many relation with occurence at other entitas.

EXAMPLE OF CARDINALITY

NOTATION (DIAGRAM E-R)
Symbolic notation in diagram of ER is:
- Square of length express gathering of entitas
- Radian express attribute
- Rhombic of relationship gathering expressing
- Mark with lines as link between relationship gathering with gathering of entitas gathering and of Entitas with its attribute