Databases, DP-900, Microsoft Certification

Describe Types of Databases (DP-900 Exam Prep)

 
This post is a part of the DP-900: Microsoft Azure Data Fundamentals Exam Prep Hub. 
This topic falls under these sections:
Describe core data concepts (25–30%)
   --> Identify options for data storage
      --> Describe types of databases

Note that there are 10 practice questions (with answers and explanations) for each section to help you solidify your knowledge of the material. Also, there are 2 practice tests with 60 questions each available on the hub below the exam topics section.

Databases are systems that store and manage data so applications can retrieve, update, and organize it efficiently. For DP-900, you should be familiar with the major types of databases, how they differ, and common use cases — especially in relation to Azure services.

What Is a Database?

A database is an organized collection of data that enables efficient access, management, and update of information. Databases may differ in how they model, structure, and query data depending on the data type, scale, and workload requirements.

Primary Types of Databases

At a high level, databases fall into two broad categories:

  1. Relational Databases
  2. Non-Relational Databases (NoSQL)

1. Relational Databases

Relational databases (RDBMS) store data in tables with rows and columns.

Key Features

  • Structured schema: Tables have defined columns with data types.
  • Relationships: Tables can be linked using keys (e.g., primary and foreign keys).
  • SQL Queries: Use Structured Query Language (SQL) to retrieve and manipulate data.
  • ACID transactions: Support atomicity, consistency, isolation, and durability for reliable data operations.

When to Use

  • Applications requiring strong data integrity
  • Banking, accounting, inventory systems
  • Workloads where relationships among data matter

Examples

  • Azure SQL Database
  • Azure Database for PostgreSQL
  • Azure Database for MySQL

2. Non-Relational Databases (NoSQL)

Non-relational databases, often called NoSQL databases, store data in ways that differ from traditional tables. They are generally schema-less and more flexible, which helps with scalability and handling varied data types.

Key Characteristics

  • No fixed schema
  • Designed for horizontal scaling and large data volumes
  • Support for semi-structured and unstructured data
  • Often optimized for specific access patterns

The most common NoSQL models include:

a. Key-Value Databases

Key-value stores are the simplest type of NoSQL database.

  • Data stored as pairs: key (identifier) and value (data).
  • Efficient for simple lookups when the key is known.

Use cases: Session state, caching, user preferences.

b. Document Databases

Document databases store data as documents, typically in JSON format.

  • Each document is a self-describing object with a unique ID.
  • Supports nested fields and flexible attributes.

Use cases: Content management, user profiles, web apps.

c. Column-Family (Wide-Column) Databases

Column-family databases use tables with column families — groups of related columns that can vary by row.

  • Designed for wide tables where columns are sparse.
  • Good for distributed data and analytical workloads.

Use cases: Time-series data, analytics, event logging.

d. Graph Databases

Graph databases focus on relationships between data elements.

  • Use nodes (entities) and edges (relationships).
  • Optimized for queries involving deep connections (e.g., social networks).

Use cases: Recommendation engines, fraud detection, network analysis.

Relational vs Non-Relational: A Quick Comparison

FeatureRelationalNon-Relational (NoSQL)
SchemaFixedFlexible / Schema-less
Data ModelTablesVaries (documents, keys, graphs)
Query LanguageSQLVaries by database
ScalabilityVertical scalingHorizontal scaling
Typical UseStrong consistency & relationshipsLarge, evolving, semi/unstructured data

How Azure Supports These Databases

Relational Database Services

Azure provides managed relational services:

  • Azure SQL Database: Managed SQL service
  • Azure Database for MySQL and PostgreSQL: Managed open-source options

These are ideal for structured data and transactional workloads.

Non-Relational Database Services

Azure supports NoSQL and other flexible databases:

  • Azure Cosmos DB: A globally distributed, multi-model NoSQL database service that supports document, key-value, column-family, and graph models.

This makes Cosmos DB unique in supporting multiple non-relational data models from a single service.

Why Understanding Types of Databases Matters for DP-900

On the DP-900 exam, you may be asked to:

  • Classify a database type based on a description of its structure.
  • Choose the best database model for a given business scenario.
  • Identify Azure services that match a database type.

Knowing relational vs non-relational databases, and the sub-types of NoSQL models, will help you answer these questions with confidence.

Summary — Exam-Relevant Takeaways

✔ Relational databases store structured data using tables, enforce schemas, and use SQL.
✔ NoSQL databases store non-relational data and include key-value, document, column-family, and graph types.
✔ Azure SQL Database and open-source relational offerings support structured workloads.
✔ Azure Cosmos DB supports multiple non-relational models for schema-flexible data.

Go to the Practice Exam Questions for this topic.

Go to the DP-900 Exam Prep Hub main page.

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