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Chapter 2 Data Models (INTRODUCTION) - Coggle Diagram
Chapter 2
Data Models
(INTRODUCTION)
Database Systems:
Design, Implementation, and
Management
INTRODUCTION
Designers, programmers, and end users all have distinct perspectives on data.
• Different perspectives on the same facts result in different design
They do not reflect the operations of the organisation
• Data modelling simplifies the process.
designing a database
• Various levels of data abstraction are beneficial.
harmonise different perspectives on the same data
• Data models - Relatively basic models of complicated data • Data modelling and data models
data structures in the real world
• Frequently graphical
• Model: a representation of a real-world object or concept.
Helpful in deciphering the complexity of the
environment in the real world
• Data modelling is a continuous and iterative process.
The Importance of Data Models
• Make interaction between the designer, the application programmer, and the end user easier.
• Distinct end users have different perspectives and requirements for data.
• The data model arranges information for a variety of users.
• A data model is a fictitious representation of reality.
Inability to extract essential data from the data model
Basic Building Blocks of a Data Model
• Entity: any object for which data will be collected and stored. (apa juga yang berkenaan dgn data yang
boleh disimpan
)
• An entity's attribute is a trait.
• Relationship: a term that describes a connection between two or more entities.
– Relationship of one to many (1:M)
– M:N or M:M (many-to-many) relationship
– A one-to-one relationship (1:1)
• Data constraint (KEKANGAN) : a limitation imposed on the data
• Attribute: a characteristic of an entity (ciri-ciri yang terdapat pada entiti)
CTH
dalam setiap ciri-ciri, mesti ada ciri-ciri yang unik. Contoh: nombor matrik, nombor ic, kod kursus
Entity : - Kelas
Attribute : - Nama kelas, Kod kelas