Azure Database Services

Azure SQL (Relational/SQL-based)

SQL Server (The Engine/Software): This is a Relational Database Management System (RDBMS) developed by Microsoft. It is the “brain” or software application that processes queries, manages security, and handles how data is stored on disks. You can install SQL Server on Windows or Linux servers.
SQL Database (The Data Store): A database is the actual collection of tables, rows, and columns where your information lives. One SQL Server can host hundreds or thousands of individual SQL Databases.

Microsoft’s flagship SQL family for cloud workloads:

Service	Description
Azure SQL Database	Fully managed, serverless PaaS SQL database
Azure SQL Database Hyperscale	For very large databases (up to 100TB+)
Azure SQL Managed Instance	Full SQL Server compatibility in the cloud
SQL Server on Azure VMs	IaaS; full control over SQL Server on a virtual machine

For modern, cloud-native app development:

Service	Description
Azure Cosmos DB	Globally distributed, multi-model NoSQL database
Azure Database for PostgreSQL Flexible Servers	Managed open-source PostgreSQL

For migrating or extending legacy systems:

Service	Description
Azure Database for MySQL Flexible Servers	Managed MySQL
Azure DocumentDB (MongoDB compatibility)	NoSQL with MongoDB API support
Azure Managed Instance for Apache Cassandra	Managed Cassandra clusters
MongoDB Atlas (Partner)	Third-party MongoDB service integrated in Azure
Oracle AI Database@Azure	Oracle DB running natively on Azure infrastructure

For on-premises + cloud hybrid scenarios:

Service	Description
Azure Arc data controllers	Manage data services across environments
SQL Managed Instances – Azure Arc	Run SQL MI anywhere via Arc
SQL Server instances	Extend on-prem SQL Servers with Azure capabilities

Supporting tools and services:

Service	Description
Azure Cache for Redis	In-memory caching layer for performance
Azure Database Migration Services	Migrate databases to Azure
Elastic Job Agents	Scheduled job execution across SQL databases
Managed Databases	Simplified database management interface
Azure Managed Redis	Fully managed Redis service

Need	Recommended Service
Traditional SQL workloads	Azure SQL Database
Massive scale NoSQL	Cosmos DB
Open-source MySQL/PostgreSQL	Flexible Servers
MongoDB compatibility	DocumentDB
Hybrid/on-prem integration	Azure Arc services
Performance caching	Azure Cache for Redis
Database migration	Azure Database Migration Services