Data Modeling

Data modeling is the process of creating a data model for the data to be stored in a Database
This data model is a conceptual representation of
- Data objects
- The associations between different data objects
- The rules
Data model emphasizes on what data is needed and how it should be organized instead of what operations need to be performed on the data
The two types of Data Models techniques are
- Entity Relationship (E-R) Model
- UML (Unified Modelling Language)
Types of Data Models
- Conceptual: This Data Model defines WHAT the system contains
  - The purpose is to organize, scope and define business concepts and rules
- Logical: Defines HOW the system should be implemented regardless of the DBMS
  - The purpose is to developed technical map of rules and data structures
- Physical: This Data Model describes HOW the system will be implemented using a specific DBMS system
  - The purpose is actual implementation of the database

What is Data Modeling

A data model is used to document, define, organize, and show how the data structures within a given database, architecture, application, or platform are connected, stored, accessed, and processed within the given system and between other systems

Data modeling occurs at three levels—physical, logical, and conceptual
- A physical model is a schema or framework for how data is physically stored in a database
- A conceptual model identifies the high-level, user view of data
- A logical data model sits between the physical and conceptual levels and allows for the logical representation of data to be separate from its physical storage
Relationships between entities can be one-to-one, one-to-many, or many-to-many
There are three parts to the entity integrity rule:
- All entities should have a primary key
- The values of all primary keys must be unique
- The value of a primary key cannot be null