What is the Azure SQL Database service?

Azure SQL Database is a general-purpose relational database, provided as a managed service. With it, you can create a highly available and high-performance data storage layer for the applications and solutions in Azure. SQL Database can be the right choice for a variety of modern cloud applications because it enables you to process both relational data and non-relational structures, such as graphs, JSON, spatial, and XML.

It's based on the latest stable version of the Microsoft SQL Server database engine. You can use advanced query processing features, such as high-performance in-memory technologies and intelligent query processing. In fact, the newest capabilities of SQL Server are released first to SQL Database, and then to SQL Server itself. You get the newest SQL Server capabilities with no overhead for patching or upgrading, tested across millions of databases.

SQL Database enables you to easily define and scale performance within two different purchasing models: a vCore-based purchasing model and a DTU-based purchasing model. SQL Database is a fully managed service that has built-in high availability, backups, and other common maintenance operations. Microsoft handles all patching and updating of the SQL and operating system code. You don't have to manage the underlying infrastructure.

Note

For relevant terms and their definitions, see the SQL Database terms glossary.

Deployment models

Azure SQL Database provides the following deployment options for an Azure SQL database:

Diagram of deployment options

  • Single database represents a fully managed, isolated database. You might use this option if you have modern cloud applications and microservices that need a single reliable data source. A single database is similar to a contained database in Microsoft SQL Server Database Engine.
  • Managed instance is a fully managed instance of the Microsoft SQL Server Database Engine. It contains a set of databases that can be used together. Use this option for easy migration of on-premises SQL Server databases to the Azure cloud, and for applications that need to use the database features that SQL Server Database Engine provides.
  • Elastic pool is a collection of single databases with a shared set of resources, such as CPU or memory. Single databases can be moved into and out of an elastic pool.

Important

To understand the feature differences between SQL Database and SQL Server, as well as the differences among different Azure SQL Database deployment options, see SQL Database features.

SQL Database delivers predictable performance with multiple resource types, service tiers, and compute sizes. It provides dynamic scalability with no downtime, built-in intelligent optimization, global scalability and availability, and advanced security options. These capabilities allow you to focus on rapid app development and accelerating your time-to-market, rather than on managing virtual machines and infrastructure. The SQL Database service is currently in 38 datacenters around the world, so you can run your database in a datacenter near you.

Scalable performance and pools

You can define the amount of resources assigned.

  • With single databases, each database is isolated from others and is portable. Each has its own guaranteed amount of compute, memory, and storage resources. The amount of the resources assigned to the database is dedicated to that database, and isn't shared with other databases in Azure. You can dynamically scale single database resources up and down. The single database option provides different compute, memory, and storage resources for different needs. For example, you can get 1 to 80 vCores, or 32 GB to 4 TB. The hyperscale service tier for single database enables you to scale to 100 TB, with fast backup and restore capabilities.
  • With elastic pools, you can assign resources that are shared by all databases in the pool. You can create a new database, or move the existing single databases into a resource pool to maximize the use of resources and save money. This option also gives you the ability to dynamically scale elastic pool resources up and down.
  • With managed instances, each managed instance is isolated from other instances with guaranteed resources. Within a managed instance, the instance databases share a set of resources. You can dynamically scale managed instance resources up and down.

You can build your first app on a small, single database at a low cost per month in the general-purpose service tier. You can then change its service tier manually or programmatically at any time to the business-critical service tier, to meet the needs of your solution. You can adjust performance without downtime to your app or to your customers. Dynamic scalability enables your database to transparently respond to rapidly changing resource requirements. You pay for only the resources that you need when you need them.

Dynamic scalability is different from autoscale. Autoscale is when a service scales automatically based on criteria, whereas dynamic scalability allows for manual scaling without downtime. The single database option supports manual dynamic scalability, but not autoscale. For a more automatic experience, consider using elastic pools, which allow databases to share resources in a pool based on individual database needs. Another option is to use scripts that can help automate scalability for a single database. For an example, see Use PowerShell to monitor and scale a single database.

Purchasing models

SQL Database offers the following purchasing models:

  • The vCore-based purchasing model lets you choose the number of vCores, the amount of memory, and the amount and speed of storage. The vCore-based purchasing model also allows you to use Azure Hybrid Benefit for SQL Server to gain cost savings. For more information about the Azure Hybrid Benefit, see the "Frequently asked questions" section later in this article.
  • The DTU-based purchasing model offers a blend of compute, memory, and I/O resources in three service tiers, to support light to heavy database workloads. Compute sizes within each tier provide a different mix of these resources, to which you can add additional storage resources.
  • The serverless model automatically scales compute based on workload demand, and bills for the amount of compute used per second. The serverless compute tier also automatically pauses databases during inactive periods when only storage is billed, and automatically resumes databases when activity returns.

Service tiers

Azure SQL Database offers three service tiers that are designed for different types of applications:

  • General Purpose/Standard service tier designed for common workloads. It offers budget-oriented balanced compute and storage options.
  • Business Critical/Premium service tier designed for OLTP applications with high transaction rate and lowest-latency I/O. It offers the highest resilience to failures by using several isolated replicas.
  • Hyperscale service tier designed for very large OLTP database and the ability to auto-scale storage and scale compute fluidly.

Elastic pools to maximize resource utilization

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. Unpredictable usage patterns can make it hard to manage costs and your business model. Elastic pools are designed to solve this problem. You allocate performance resources to a pool rather than an individual database. You pay for the collective performance resources of the pool rather than for single database performance.

Graphic that shows elastic pools in basic, standard, and premium editions

With elastic pools, you don’t need to focus on dialing database performance up and down as demand for resources fluctuates. The pooled databases consume the performance resources of the elastic pool as needed. Pooled databases consume but don’t exceed the limits of the pool, so your cost remains predictable even if individual database usage doesn’t.

You can add and remove databases to the pool, scaling your app from a handful of databases to thousands, all within a budget that you control. You can also control the minimum and maximum resources available to databases in the pool, to ensure that no database in the pool uses all the pool resources, and that every pooled database has a guaranteed minimum amount of resources. To learn more about design patterns for software as a service (SaaS) applications that use elastic pools, see Design patterns for multi-tenant SaaS applications with SQL Database.

Scripts can help with monitoring and scaling elastic pools. For an example, see Use PowerShell to monitor and scale a SQL elastic pool in Azure SQL Database.

Important

A managed instance doesn't support elastic pools. Rather, a managed instance is a collection of instance databases that share managed instance resources.

Blend single databases with pooled databases

You can blend single databases with elastic pools, and change the service tiers of single databases and elastic pools to adapt to your situation. You can also mix and match other Azure services with SQL Database to meet your unique app design needs, drive cost and resource efficiencies, and unlock new business opportunities.

Extensive monitoring and alerting capabilities

Azure SQL Database provides advanced monitoring and troubleshooting features that help you get deeper insights into workload characteristics. These features and tools include:

  • The built-in monitoring capabilities provided by the latest version of SQL Server Database Engine. They enable you to find real-time performance insights.
  • PaaS monitoring capabilities provided by Azure that enable you to monitor and troubleshoot a large number of database instances.

Query Store, a built-in SQL Server monitoring feature, records the performance of your queries in real time, and enables you to identify the potential performance issues and the top resource consumers. Automatic tuning and recommendations provide advice regarding the queries with the regressed performance and missing or duplicated indexes. Automatic tuning in SQL Database enables you to either manually apply the scripts that can fix the issues, or let SQL Database apply the fix. SQL Database can also test and verify that the fix provides some benefit, and retain or revert the change depending on the outcome. In addition to Query Store and automatic tuning capabilities, you can use standard DMVs and XEvent to monitor the workload performance.

Azure provides built-in performance monitoring and alerting tools, combined with performance ratings, that enable you to monitor the status of thousands of databases. Using these tools, you can quickly assess the impact of scaling up or down, based on your current or projected performance needs. Additionally, SQL Database can emit metrics and diagnostic logs for easier monitoring. You can configure SQL Database to store resource usage, workers and sessions, and connectivity into one of these Azure resources:

  • Azure Storage: For archiving vast amounts of telemetry for a small price.
  • Azure Event Hubs: For integrating SQL Database telemetry with your custom monitoring solution or hot pipelines.
  • Azure Monitor logs: For a built-in monitoring solution with reporting, alerting, and mitigating capabilities.

Diagram of Azure monitoring architecture

Availability capabilities

In a traditional SQL Server environment, you generally have at least two machines locally set up. These machines have exact, synchronously maintained, copies of the data to protect against a failure of a single machine or component. This environment provides high availability, but it doesn't protect against a natural disaster destroying your datacenter.

Disaster recovery assumes that a catastrophic event is geographically localized enough to have another machine or set of machines with a copy of your data far away. In SQL Server, you can use Always On Availability Groups running in async mode to get this capability. People often don't want to wait for replication to happen that far away before committing a transaction, so there's potential for data loss when you do unplanned failovers.

Databases in the premium and business critical service tiers already do something very similar to the synchronization of an availability group. Databases in lower service tiers provide redundancy through storage by using a different but equivalent mechanism. Built-in logic helps protect against a single machine failure. The active geo-replication feature gives you the ability to protect against disaster where a whole region is destroyed.

Azure Availability Zones tries to protect against the outage of a single datacenter building within a single region. It helps you protect against the loss of power or network to a building. In SQL Database, you place the different replicas in different availability zones (different buildings, effectively).

In fact, the service level agreement (SLA) of Azure, powered by a global network of Microsoft-managed datacenters, helps keep your app running 24/7. The Azure platform fully manages every database, and it guarantees no data loss and a high percentage of data availability. Azure automatically handles patching, backups, replication, failure detection, underlying potential hardware, software or network failures, deploying bug fixes, failovers, database upgrades, and other maintenance tasks. Standard availability is achieved by a separation of compute and storage layers. Premium availability is achieved by integrating compute and storage on a single node for performance, and then implementing technology similar to Always On Availability Groups. For a full discussion of the high availability capabilities of Azure SQL Database, see SQL Database availability.

In addition, SQL Database provides built-in business continuity and global scalability features. These include:

  • Automatic backups:

    SQL Database automatically performs full, differential, and transaction log backups of SQL databases to enable you to restore to any point in time. For single databases and pooled databases, you can configure SQL Database to store full database backups to Azure Storage for long-term backup retention. For managed instances, you can also perform copy-only backups for long-term backup retention.

  • Point-in-time restores:

    All SQL Database deployment options support recovery to any point in time within the automatic backup retention period for any SQL database.

  • Active geo-replication:

    The single database and pooled databases options allow you to configure up to four readable secondary databases in either the same or globally distributed Azure datacenters. For example, if you have a SaaS application with a catalog database that has a high volume of concurrent read-only transactions, use active geo-replication to enable global read scale. This removes bottlenecks on the primary that are due to read workloads. For managed instances, use auto-failover groups.

  • Auto-failover groups:

    All SQL Database deployment options allow you to use failover groups to enable high availability and load balancing at global scale. This includes transparent geo-replication and failover of large sets of databases, elastic pools, and managed instances. Failover groups enable the creation of globally distributed SaaS applications, with minimal administration overhead. This leaves all the complex monitoring, routing, and failover orchestration to SQL Database.

  • Zone-redundant databases:

    SQL Database allows you to provision premium or business critical databases or elastic pools across multiple availability zones. Because these databases and elastic pools have multiple redundant replicas for high availability, placing these replicas into multiple availability zones provides higher resilience. This includes the ability to recover automatically from the datacenter scale failures, without data loss.

Built-in intelligence

With SQL Database, you get built-in intelligence that helps you dramatically reduce the costs of running and managing databases, and that maximizes both performance and security of your application. Running millions of customer workloads around the clock, SQL Database collects and processes a massive amount of telemetry data, while also fully respecting customer privacy. Various algorithms continuously evaluate the telemetry data so that the service can learn and adapt with your application.

Automatic performance monitoring and tuning

SQL Database provides detailed insight into the queries that you need to monitor. SQL Database learns about your database patterns, and enables you to adapt your database schema to your workload. SQL Database provides performance tuning recommendations, where you can review tuning actions and apply them.

However, constantly monitoring a database is a hard and tedious task, especially when dealing with many databases. Intelligent Insights does this job for you by automatically monitoring SQL Database performance at scale. It informs you of performance degradation issues, it identifies the root cause of each issue, and provides performance improvement recommendations when possible.

Managing a huge number of databases might be impossible to do efficiently even with all available tools and reports that SQL Database and Azure provide. Instead of monitoring and tuning your database manually, you might consider delegating some of the monitoring and tuning actions to SQL Database by using automatic tuning. SQL Database automatically applies recommendations, tests, and verifies each of its tuning actions to ensure the performance keeps improving. This way, SQL Database automatically adapts to your workload in a controlled and safe way. Automatic tuning means that the performance of your database is carefully monitored and compared before and after every tuning action. If the performance doesn’t improve, the tuning action is reverted.

Many of our partners that run SaaS multi-tenant apps on top of SQL Database are relying on automatic performance tuning to make sure their applications always have stable and predictable performance. For them, this feature tremendously reduces the risk of having a performance incident in the middle of the night. In addition, because part of their customer base also uses SQL Server, they're using the same indexing recommendations provided by SQL Database to help their SQL Server customers.

Two automatic tuning aspects are available in SQL Database:

  • Automatic index management: Identifies indexes that should be added in your database, and indexes that should be removed.
  • Automatic plan correction: Identifies problematic plans and fixes SQL plan performance problems.

Adaptive query processing

You can use adaptive query processing, including interleaved execution for multi-statement table-valued functions, batch mode memory grant feedback, and batch mode adaptive joins. Each of these adaptive query processing features applies similar “learn and adapt” techniques, helping further address performance issues related to historically intractable query optimization problems.

Advanced security and compliance

SQL Database provides a range of built-in security and compliance features to help your application meet various security and compliance requirements.

Important

Microsoft has certified Azure SQL Database (all deployment options) against a number of compliance standards. For more information, see the Microsoft Azure Trust Center, where you can find the most current list of SQL Database compliance certifications.

Advance threat protection

Advanced data security is a unified package for advanced SQL security capabilities. It includes functionality for discovering and classifying sensitive data, managing your database vulnerabilities, and detecting anomalous activities that might indicate a threat to your database. It provides a single location for enabling and managing these capabilities.

  • Data discovery and classification:

    This feature provides capabilities built into Azure SQL Database for discovering, classifying, labeling, and protecting the sensitive data in your databases. It provides visibility into your database classification state, and tracks the access to sensitive data within the database and beyond its borders.

  • Vulnerability assessment:

    This service can discover, track, and help you remediate potential database vulnerabilities. It provides visibility into your security state, and includes actionable steps to resolve security issues, and enhance your database fortifications.

  • Threat detection:

    This feature detects anomalous activities that indicate unusual and potentially harmful attempts to access or exploit your database. It continuously monitors your database for suspicious activities, and provides immediate security alerts on potential vulnerabilities, SQL injection attacks, and anomalous database access patterns. Threat detection alerts provide details of the suspicious activity, and recommend action on how to investigate and mitigate the threat.

Auditing for compliance and security

Auditing tracks database events and writes them to an audit log in your Azure storage account. Auditing can help you maintain regulatory compliance, understand database activity, and gain insight into discrepancies and anomalies that might indicate business concerns or suspected security violations.

Data encryption

SQL Database helps secure your data by providing encryption. For data in motion, it uses transport layer security. For data at rest, it uses transparent data encryption. For data in use, it uses always encrypted.

Azure Active Directory integration and multi-factor authentication

SQL Database enables you to centrally manage identities of database user and other Microsoft services with Azure Active Directory integration. This capability simplifies permission management and enhances security. Azure Active Directory supports multi-factor authentication to increase data and application security, while supporting a single sign-in process.

Easy-to-use tools

SQL Database makes building and maintaining applications easier and more productive. SQL Database allows you to focus on what you do best: building great apps. You can manage and develop in SQL Database by using tools and skills you already have.

  • The Azure portal:

    A web-based application for managing all Azure services.

  • SQL Server Management Studio:

    A free, downloadable client application for managing any SQL infrastructure, from SQL Server to SQL Database.

  • SQL Server Data Tools in Visual Studio:

    A free, downloadable client application for developing SQL Server relational databases, SQL databases, Integration Services packages, Analysis Services data models, and Reporting Services reports.

  • Visual Studio Code:

    A free, downloadable, open-source code editor for Windows, macOS, and Linux. It supports extensions, including the mssql extension for querying Microsoft SQL Server, Azure SQL Database, and Azure SQL Data Warehouse.

SQL Database supports building applications with Python, Java, Node.js, PHP, Ruby, and .NET on macOS, Linux, and Windows. SQL Database supports the same connection libraries as SQL Server.

Create and manage Azure SQL resources with the Azure portal

The Azure portal provides a single page where you can manage all of your Azure SQL resources including your SQL virtual machines.

To access the Azure SQL resources page, select Azure SQL in the left-hand menu of the Azure portal. If Azure SQL is not in the list, select All services, then type Azure SQL in the search box.

Note

Azure SQL provides a quick and easy way to access all of your SQL databases, elastic pools, database servers, SQL managed instances, and SQL virtual machines. Azure SQL is not a service or resource.

To manage existing resources, select the desired item in the list. To create new Azure SQL resources, select + Add.

Azure SQL portal page

After selecting + Add, view additional information about the different options by selecting Show details on any tile.

databases tile details

For details, see:

SQL Database frequently asked questions

What is the current version of SQL Database?

The current version of SQL Database is V12. Version V11 has been retired.

Can I control when patching downtime occurs?

No. The impact of patching is generally not noticeable if you employ retry logic in your app. For more information, see Planning for Azure maintenance events in Azure SQL Database.

Azure Hybrid Benefit questions

Are there dual-use rights with Azure Hybrid Benefit for SQL Server?

You have 180 days of dual use rights of the license to ensure migrations are running seamlessly. After that 180-day period, you can only use the SQL Server license in the cloud in SQL Database. You no longer have dual use rights on-premises and in the cloud.

How does Azure Hybrid Benefit for SQL Server differ from license mobility?

We offer license mobility benefits to SQL Server customers with Software Assurance. This allows reassignment of their licenses to a partner's shared servers. You can use this benefit on Azure IaaS and AWS EC2.

Azure Hybrid Benefit for SQL Server differs from license mobility in two key areas:

  • It provides economic benefits for moving highly virtualized workloads to Azure. SQL Server Enterprise Edition customers can get four cores in Azure in the General Purpose SKU for every core they own on-premises for highly virtualized applications. License mobility doesn't allow any special cost benefits for moving virtualized workloads to the cloud.
  • It provides for a PaaS destination on Azure (SQL Database managed instance) that's highly compatible with SQL Server on-premises.

What are the specific rights of the Azure Hybrid Benefit for SQL Server?

SQL Database customers have the following rights associated with Azure Hybrid Benefit for SQL Server:

License footprint What does Azure Hybrid Benefit for SQL Server get you?
SQL Server Enterprise Edition core customers with SA
  • Can pay base rate on either General Purpose or Business Critical SKU

  • 1 core on-premises = 4 cores in General Purpose SKU

  • 1 core on-premises = 1 core in Business Critical SKU
  • SQL Server Standard Edition core customers with SA
  • Can pay base rate on General Purpose SKU only

  • 1 core on-premises = 1 core in General Purpose SKU
  • Engage with the SQL Server engineering team

    Next steps