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
ERD is a model of a network that uses word order is stored in the abstract system.
Differences between the DFD and ERD, namely:
1. DFD is a model of network functions that will be implemented by the system.
2. ERD is a model that emphasizes the network data on the structure and relationship data.
ELEMENT in 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
In the ER diagram, the relationship can be described with a rhomb. 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 the relation.
RELATIONSHIP DEGREE
Relationship degree is the number of entities which participating in a relationship. Degree is unit which is often used in the ERD.
ATTRIBUTE
Attribute is the nature or characteristics of each entity and relationship
CARDINALITY
Cardinality indicates the maximum number of record/tuple that can be relation with the entity on the other entity
DEGREE OF RELATIONSHIP
- Unary relationship
is the relationship model between the entity originating from the same entity set.
- Binary relationship
is the relationship model between 2 entities
- Ternary relationship
is a relationship between the instance of 3 types of entities are unilateral
NOTATION (E-R DIAGRAM)
Symbolic notation in the ER diagram, namely :
1. Rectangle represent the collective entity
2. Circle represent the attributes
3. Rhomb represent collective relationships
4. Line as the set of relationships between the entity and the collective entity with the attribute
Reference:
1. Agus Sanjaya ER, S.Kom, M.Kom, slide presentation : Database and ER-Diagram
