What is Azure SQL Database?

Azure SQL Database is a fully managed platform as a service (PaaS) database engine that handles most of the database management functions such as upgrading, patching, backups, and monitoring without user involvement.

What is a single database in Azure SQL Database?

The single database resource type creates a database in Azure SQL Database with its own set of resources and is managed via a server. With a single database, each database is isolated and portable. Each has its own service tier within the DTU-based purchasing model or vCore-based purchasing model and a guaranteed compute size.

What are SQL elastic pools?

Elastic pool is a collection of a single database with a shared set of resources, such as CPU or memory. Single databases can be moved into and out of an elastic pool.

Azure SQL Database elastic pools are a simple, cost-effective solution for managing and scaling multiple databases that have varying and unpredictable usage demands. The databases in an elastic pool are on a single server and share a set number of resources at a set price. Elastic pools in Azure SQL Database enable SaaS developers to optimize the
price performance for a group of databases within a prescribed budget while delivering performance elasticity for each database.

Single databases vs elastic pools

A single database can be moved into or out of an elastic pool for resource sharing. For many businesses and applications, being able to create single databases and dial performance up or down on demand is enough, especially if usage patterns are relatively predictable. But if you have unpredictable usage patterns, it can make it hard to manage costs and your business model. Elastic pools are designed to solve this problem. The concept is simple. You allocate performance resources to a pool rather than an individual database and pay for the collective performance resources of the pool rather than for single database performance.