In Azure, you can have your SQL Server workloads running as a hosted service (PaaS), or a hosted infrastructure (IaaS). Within PaaS, you have multiple deployment options and service tiers within each deployment option. The key question that you need to ask when deciding between PaaS or IaaS is do you want to manage your database, apply patches, and take backups, or do you want to delegate these operations to Azure.
Databases offer the following deployment options:
As A Single Database
with its own set of resources managed via a database server. A single database is similar to a contained database in SQL Server. This option is optimized for modern application development of new cloud-born applications. Hyperscale and serverless options are available.
An Elastic Pool
which is a collection of databases with a shared set of resources managed via a database server. Single databases can be moved into and out of an elastic pool. This option is optimized for modern application development of new cloud-born applications using the multi-tenant SaaS application pattern. Elastic pools provide a cost-effective solution for managing the performance of multiple databases that have variable usage patterns.
A Database Server
which is used to manage groups of single databases and elastic pools. Database servers act as a central administrative point for multiple single or pooled databases, logins, firewall rules, auditing rules, threat detection policies, and failover groups.
AZURE SQL or SQL Server: which one is appropriate?
Azure SQL is a cloud service built on the SQL Server line, so it shares many features with local SQL Server.
Differences Between SQL Server and Azure SQL
Azure SQL is based on SQL Server and has many similarities in functionality and compatibility. But that does not mean they are the same. In fact, contrary to what many people think, Azure SQL is different from the cloud version of SQL Server. Indeed, there are many fundamental differences between the two.
It is essential to understand the fundamentals before moving on to the exact difference. In SQL Server, the database is the only entity on the database server, but in SQL Azure, a single database can host different client databases. In other words, Azure SQL is multi-tenant and shares physical resources with all clients using this service.