Database - rahul7838/quora.clone GitHub Wiki

Schema and Data Model

A database schema is the formal structure and organization of a database, defining:

Tables, columns, and their data types

Relationships between tables

Constraints (primary keys, foreign keys, unique constraints)

Views and indexes

• A database data model is a higher-level conceptual representation that:

Describes how data is organized, accessed, and related

Can be implemented through different schemas Examples include relational, hierarchical, network, and object-oriented models

Key differences:

Abstraction level: Data models are conceptual frameworks, while schemas are concrete implementations

Scope: Models define overall architecture; schemas specify detailed technical requirements

Purpose: Models guide database design; schemas enforce data structure and relationships

For example, a relational data model might be implemented through different SQL schemas depending on specific requirements and optimizations needed.

Different Data Model

A database data model is a theoretical framework that determines how data will be stored, organized, and manipulated. The key data models are:

Relational Model

Data organized in tables (relations)

Uses SQL

Example schema: Customer table linked to Orders table via foreign key

Hierarchical Model

Data organized in tree structure

Parent-child relationships

Example schema: XML database with nested elements

Network Model

Data organized in graph structure

Many-to-many relationships

Example schema: Flight routes database where cities connect to multiple other cities

Object-Oriented Model

Data organized as objects with attributes and methods

Inheritance and encapsulation

Example schema: Java objects stored directly in database

Each model can be implemented through different schemas based on specific needs. For example, a relational model for an e-commerce system could have different schemas:

Normalized schema (separate tables for products, categories, prices)

Denormalized schema (combined tables for faster querying)

Hybrid schema (mix of normalized and denormalized)