Service Editions and Tiers
Microsoft uses editions for SQL Server and service tiers for Azure SQL Database to provide combinations of product features, performance, and price levels so that you can select one that best meets your application’s requirements.
https://docs.microsoft.com/en-us/azure/sql-database/sql-database-paas-vs-sql-server-iaas
SQL Server 2016 is available in the following editions:
Express This edition is a free version of SQL Server with limited features that you can use for small applications and Web sites. The maximum database size supported by this edition is 10 GB. It uses up to 1 GB memory and to the lesser of 1 physical processor or 4 cores. There are three types of SQL Server 2016 Express from which to choose:
LocalDB You use LocalDB for a simple application with a local embedded database that runs in single-user mode.
Express You use Express when your application requires a small database only and does not require any other components packaged with SQL Server in the Standard edition. You can install this edition on a server and then enable remote connections to support multiple users.
Express with Advanced Services This edition includes the database engine as well as Full Text Search and Reporting Services.
Web This edition is scalable up to 64 GB of memory and the lesser of 4 physical processors or 16 cores with a maximum database size of 524 PB. It includes the database engine, but without support for availability groups and other high availability features. It also does not include many of the advanced security and replication features available in Standard or Enterprise edition, nor does it include the business intelligence components such as Analysis Services and Reporting Services, among others. Web edition is intended for use only by Web hosters and third-party software service providers.
Standard This edition scales to 128 GB of memory and the lesser of 4 physical processors or 24 cores. The maximum database size with Standard edition is 524 PB. This edition includes core database and business intelligence functionality and includes basic high-availability and disaster recovery features, new security features such as row-level security and dynamic data masking, and access to non-relational data sources by using JSON and PolyBase.
Enterprise This edition includes all features available in the SQL Server platform and provides the highest scalability, greatest number of security features, and the most advanced business intelligence and analytics features. Like Standard edition, Enterprise edition supports a database size up to 524 PB, but its only limits on memory and processor sizes are the maximums set by your operating system. To support higher availability, this edition supports up to 8 secondary replicas, with up to two synchronous secondary replicas, in an availability group, online page and file restore, online indexing, fast recovery, mirrored backups, and the ability to hot add memory and CPU. For greater performance, Enterprise edition supports in-memory OLTP, table and index partitioning, data compression, Resource Governor, parallelism for partitioned tables, multiple file stream containers, and delayed durability, among other features. Enterprise edition includes many security features not found in Standard edition. In particular, Always Encrypted protects data at rest and in motion. Additional security features exclusive to Enterprise edition include more finely-grained auditing, transparent data encryption, and extensible key management. Features supporting data warehouse operations found only in Enterprise edition include change data capture, star join query optimizations, and parallel query processing on partitioned indexes and tables.
Developer This edition is for developers that create, test, and demonstrate applications using any of the data platform components available in Enterprise edition. However, the Developer edition cannot be used in a production environment.
Evaluation This edition is a free trial version of SQL Server 2016. You can use this for up to 180 days that you can use to explore all of the features available in Enterprise Edition before making a purchasing decision.
https://docs.microsoft.com/en-us/sql/sql-server/editions-and-components-of-sql-server-version-15?view=sql-server-ver15
When you select the type of SQL Database to implement, you choose a service tier along with a performance level. The service tier sets the maximum database size while the performance level determines the amount of CPU, memory, and IO thresholds which collectively are measured as a DTU.
When you create a new SQL Database, you can choose from the following service tiers:
Basic This service tier has a maximum database size of 2 GB and performance level of 5 DTUs. You use this option when you need a small database for an application or website with relatively few concurrent requests. The benchmark transaction rate is 16,600 transactions per hour.
Standard This service tier has a maximum database size of 250 GB and performance levels ranging from 10 to 100 DTUs. You can use this option when a database needs to support multiple applications and multiple concurrent requests for workgroup and web applications. With 50 DTUs, the benchmark transaction rate is 2,570 transactions per minute.
Premium This service tier has a maximum database size of 1 TB and performance levels ranging from 125 to 4,000 DTUs. You use this option for enterprise-level database requirements. With 1,000 DTUs, the benchmark transaction rate is 735 transactions per second.
https://social.technet.microsoft.com/wiki/contents/articles/51637.azure-sql-service-tiers-and-dtus.aspx
Example 1:
Answer 1:
Example 2:
You have a 3-TB database. The database server has 64 CPU cores. You plan to migrate the database to Microsoft Azure SQL Database. You need to select the service tier for the Azure SQL database. The solution must meet or exceed the current processing capacity.
Solution: You select the Premium service tier.
Basic: 2GB maximum storage / 5 maximum DTUs
Standard: 1TB maximum storage / 3000 maximum DTUs
Premium: 4TB maximum storage / 4000 maximum DTUs