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❝ Explore Relational Databse Component ❞

posted on Thursday, 13 February 2014 @ 2/13/2014 12:49:00 am | permalink

Assalammualaikum.

*Note aku semua dalam English.

Database design

Conceptual databse design. The technology neutral study of data.

Conceptual databse design components.

Entity an 'object' about which data is collected, a person, place, event, actual physical object or simply a concept.
instance : an individual occurrence of an entity.
external entity : an entity, exchange data but which is not stored in the databse.

ATTRIBUTE

A unit fact about a particular entity the face should be (something error)(indivisible)

Relationship

An association among entities (see relationship section).
A procedure or a standard on organization uses and which dictales certain controls on the data, often implemented in database as a constrains.

Maximum cordinality : the max number of instances one entity can be associated with.
Minimum cordinality : The minimum number of instances one entity can be associated with.

Transferable a relationship is transferable if the parent may change over time
one to one : conditional in one direction menas that a corresponding record may or not found on the optional side
Conditional in both direction means that corresponding records may or not be found in both sides of the relay
mandatory in one direction means that a corresponding record must exist
one to many : indicates that a record in one table may be related to many (usually ot2) records in another table.

ERD's (entity relationship diagrams)

Graphical data model
entities one represented as rectangles
unique indentifier (primary key) located in rectangles at top of the entitiy rectangle is a unique identifier for employee.

RELATIONSHIP

Zero or one
exactly one
one or more
zero or more

Business rule are not usually included in the ERD graphic but are often included as text attachments.

LOGICAL DATABASE DESIGN COMPONENTS

Table a2-Dlogical structure like a grid

to be continue.........