AWS Certified Cloud Practitioner / Databases & Analytics

Databases Introduction

🗄️ What is a Database?

AWS storage services like S3, EBS, and EFS are great for files — images, PDFs, videos. But they don't understand how files relate to each other.

A database goes further. It stores data in a structured way so you can:

  • Search and retrieve info fast

  • Index for quicker queries

  • Link related data together

  • Manage large volumes efficiently

📁 Storage vs 🗄️ Database

File storage (S3, EBS, EFS) — just create, read, update, delete files. No relationships understood.

Databases — understand structure and relationships.

Example: an online store has a Customers table and an Orders table. The database knows Order 5001 belongs to Customer 101 (John) — a relationship, not just two separate files.

🧩 Types of Databases

Every database type has its own data model, strengths, and limits. The key exam skill: matching the right database to the right use case.

🗃️ Relational Databases (SQL)

Think of an Excel sheet — rows, columns, tables. Relational databases work the same way, but let you link tables together.

Example:

  • Students table has a Department ID

  • Departments table also has Department ID

  • That shared key connects the two

You can keep linking — Students ↔ Subjects, and so on — using keys as the glue. This linking is why they're called relational.

💬 SQL (Structured Query Language)

Used to insert, update, delete, and search data.

This query retrieves all students from the Students table.

🧠 Exam tip: See "SQL" → think Relational Database.

📄 NoSQL Databases & Why use NoSQL

NoSQL = "Not Only SQL." No fixed tables — built for flexibility and scale.

1. 🔀 Flexible schema

Data can be nested (like JSON), and fields can change over time — no rigid table structure.

{
  "name": "John",
  "address": { "city": "Nairobi", "country": "Kenya" },
  "cars": ["Ford", "BMW"]
}

2. 📈 Easier scaling

  • Relational DBs scale vertically → bigger server

  • NoSQL scales horizontally → more servers

3. ⚡ High performance

Optimized for specific workloads — fast, distributed, purpose-built.

🔖 NoSQL Flavors

Type

Icon

Best for

Key-Value

🔑

Simple lookups (User123 → data)

Document

📄

JSON-style nested records

Graph

🔗

Relationships (social networks, recommendations)

In-Memory

⚡

Caching, real-time speed

Search

🔎

Logs, analytics, full-text search