Azure offers several SQL-related services, each tailored to different use cases and requirements. Below is a comparison of Azure SQL Managed Instance, Azure SQL Database, and Azure SQL Server (often referred to as a logical SQL Server in Azure).
Azure SQL Database
1. Azure SQL Database
- Description: A fully managed, platform-as-a-service (PaaS) relational database offering. It is designed for modern cloud applications and supports single databases and elastic pools.
- Use Cases:
- Modern cloud-native applications.
- Microservices architectures.
- Applications requiring automatic scaling, high availability, and minimal management overhead.
- Key Features:
- Single database or elastic pools (shared resources for multiple databases).
- Automatic backups, patching, and scaling.
- Built-in high availability (99.99% SLA).
- Serverless compute tier for cost optimization.
- Limited SQL Server surface area (fewer features compared to Managed Instance).
- Limitations:
- No support for SQL Server Agent, Database Mail, or cross-database queries.
- Limited compatibility with on-premises SQL Server features.
- Management: Fully managed by Microsoft; users only manage the database and its resources.
Azure SQL Managed Instance
- Description: A fully managed instance of SQL Server in Azure, offering near 100% compatibility with on-premises SQL Server. It is part of the PaaS offering but provides more control and features compared to Azure SQL Database.
- Use Cases:
- Lift-and-shift migrations of on-premises SQL Server workloads.
- Applications requiring full SQL Server compatibility.
- Scenarios needing features like SQL Server Agent, cross-database queries, or linked servers.
- Key Features:
- Near 100% compatibility with SQL Server.
- Supports SQL Server Agent, Database Mail, and cross-database queries.
- Built-in high availability (99.99% SLA).
- Virtual network (VNet) integration for secure connectivity.
- Automated backups and patching.
- Limitations:
- Higher cost compared to Azure SQL Database.
- Slightly longer deployment times.
- Limited to a subset of SQL Server features (e.g., no Windows Authentication).
- Management: Fully managed by Microsoft, but users have more control over instance-level configurations.
Azure SQL Server
Description: A logical server in Azure that acts as a central administrative point for Azure SQL Database and Azure SQL Managed Instance. It is not a standalone database service but rather a management layer.
Use Cases:
- Managing multiple Azure SQL Databases or Managed Instances.
- Centralized authentication and firewall rules.
- Administrative tasks like setting up logins and managing access.
Key Features:
- Acts as a gateway for Azure SQL Database and Managed Instance.
- Supports Azure Active Directory (AAD) and SQL authentication.
- Configurable firewall rules for network security.
- Provides a connection endpoint for databases.
Limitations:
- Not a database service itself; it is a management tool.
- Does not host databases directly.
Management: Users manage the server configuration, logins, and firewall rules.
Side by side Comparison
| Feature/Aspect | Azure SQL Database | Azure SQL Managed Instance | Azure SQL Server (Logical) |
|---|---|---|---|
| Service Type | Fully managed PaaS | Fully managed PaaS | Management layer |
| Compatibility | Limited SQL Server features | Near 100% SQL Server compatibility | N/A (management tool) |
| Use Case | Cloud-native apps | Lift-and-shift migrations | Centralized management |
| High Availability | 99.99% SLA | 99.99% SLA | N/A |
| VNet Integration | Limited (via Private Link) | Supported | N/A |
| SQL Server Agent | Not supported | Supported | N/A |
| Cross-Database Queries | Not supported | Supported | N/A |
| Cost | Lower | Higher | Free (included in service) |
| Management Overhead | Minimal | Moderate | Minimal |
SQL Server’s Side-by-Side Feature: Not Available in Azure SQL
Following are list that shows SQL Server have but not available in Azure SQL Database and Azure SQL Managed Instance.
1. Instance-Level Features
| Feature | SQL Server | Azure SQL Database | Azure SQL Managed Instance |
|---|---|---|---|
| Multiple Databases Per Instance | ✅ Full support | ❌ Only single database per instance | ✅ Full support |
| Cross-Database Queries | ✅ Full support | ❌ Limited with Elastic Query | ✅ Full support |
| SQL Server Agent | ✅ Full support | ❌ Not available | ✅ Supported (with limitations) |
| PolyBase | ✅ Full support | ❌ Not available | ❌ Not available |
| CLR Integration (SQL CLR) | ✅ Full support | ❌ Not available | ✅ Supported (with limitations) |
| FileStream/FileTable | ✅ Full support | ❌ Not available | ❌ Not available |
2. Security Features
| Feature | SQL Server | Azure SQL Database | Azure SQL Managed Instance |
|---|---|---|---|
| Database Mail | ✅ Full support | ❌ Not available | ❌ Not available |
| Service Broker | ✅ Full support | ❌ Not available | ❌ Not available |
| Custom Certificates for Transparent Data Encryption (TDE) | ✅ Full support | ❌ Limited to Azure-managed keys | ❌ Limited customization |
3. Integration Services
| Feature | SQL Server | Azure SQL Database | Azure SQL Managed Instance |
|---|---|---|---|
| SSIS Integration | ✅ Full support | ❌ Requires external tools | ❌ Requires external tools |
| SSRS Integration | ✅ Full support | ❌ Not available | ❌ Not available |
| SSAS Integration | ✅ Full support | ❌ Not available | ❌ Not available |
4. Specialized Features
| Feature | SQL Server | Azure SQL Database | Azure SQL Managed Instance |
|---|---|---|---|
| Machine Learning Services (R/Python) | ✅ Full support | ❌ Not available | ❌ Not available |
| Data Quality Services (DQS) | ✅ Full support | ❌ Not available | ❌ Not available |
Conclusion
- Azure SQL Database: Ideal for new cloud-native applications or applications that don’t require full SQL Server compatibility.
- Azure SQL Managed Instance: Best for migrating on-premises SQL Server workloads to the cloud with minimal changes.
- Azure SQL Server (Logical): Used for managing and administering Azure SQL Databases and Managed Instances.
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