Definition of Database
• Collection of data which stored in magnetic disk, optical disk or other secondary storage.
• Collection of data which is linked one to other of an enterprise.(factory, govermental institution, or private section).
• Manufactur company : production planning data, actual production data, data ordering material.
• Hospital : data of patient, doctor, nurse, etc.
Database Management System
• Collection a database with software application in based of database.
• This software application is use for accessing and maintaining the database.
• The first aim of DBMS is to preparing an easy and efficient environment for using, collecting, and storing data and information.
Bit, Byte, Field
• Data bit is the part that contains the smallest value of 0 or 1.
• Bytes-bit set of bit similar.
• Field set of byte-byte similar, in the database used the term attribute.
Attribute or Field
Attribute 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
Types of Attribute
Single vs Multivalue
• Single -> only can containing mostly 1 value
• Multivalue -> can containing more than 1 value with same kind value
Atomic vs Composition
• Atomic -> cannot divided into smaller attribute
• Composition -> alliance of smaller attribute
Derived Attribute -> attribute that can be yield from other attribute value, for example age can be yield from attribute of birth datenull
Value attribute -> attribute with no value for a record
• Mandatory value attribute -> attribute that must have a value
record or tupple
• a data row inside a relation
• Consist of attribute collection which attribute interaction for advising entity or relation as detail
Record / Tuple
Record is a data line in a relationship. Record consists of a set of attribute-attribute where the attribute is an attribute-related entity or to inform the full relationship.
Entity / File
Entity is the object or objects in a certain mini world represented in the database. Entity can be:
1. Things that have physical (people, cars, houses, etc.)
2. think that there are conceptual (enterprise, employment, discipline, etc.)
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
Element key of data
Key is element of record that used for finding its in access time or can be used for identification each entity/record/row.
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.
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, 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.
The elements of ERD
Entity
• Something exist inside real system or abstract system which data stored or where are the data.
• Symbolized as square of length. There are also line symbol as link between compilation of entity with entity and compilation entity with its attribute.
Relationship
• Natural Relation happened between entity.
• Generally, given name with basic verb that facilitating for reading its relation.
• Symbolized as rhomb
Relationship degree
• Account of entity that participated inside a relationship.
• Degree is often used in ERD\
Attribute
• Characteristic of each entity or relationship
• Symbolized as circle
Cardinality
• Showing maximal account tupel that can be relation with entity in the other one.
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 unilaterall
Cardinality
There are 3 Cardinality 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 view. 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 relation with the incident on the first entity.
• Many To Many: if any incident occurs in many entity have relationships with other entities in the incident.
Exampel 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
Reference:
1. ER Ngurah Agus Sanjaya. Slide Part 5 - DATABASE DAN ER-DIAGRAM.
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