Here is a list of Azure SQL Server Database interview questions and answers, organized from basic to advanced levels:

Basic Level

1. What is Azure SQL Database?
   • Answer: Azure SQL Database is a fully managed relational database service in the Microsoft Azure cloud that provides high availability, scalability, and security features. It is based on the Microsoft SQL Server engine and supports T-SQL.
2. What are the different deployment models for Azure SQL Database?
   • Answer: The three main deployment models are:
     • Single Database: A fully managed, isolated database.
     • Elastic Pool: A collection of databases that share resources such as CPU and memory.
     • Managed Instance: A fully managed instance of the SQL Server with near-complete feature parity with on-premises SQL Server.
3. How does Azure SQL Database achieve high availability?
   • Answer: Azure SQL Database uses built-in high availability with the Always On feature, which includes automatic failover to secondary replicas, database redundancy, and backup capabilities.
4. What is DTU in Azure SQL Database?
   • Answer: DTU stands for Database Transaction Unit, a measure that combines CPU, memory, reads, and writes to provide a relative performance metric for different service tiers in Azure SQL Database.
5. Explain the difference between DTU and vCore pricing models.
   • Answer: The DTU model is a blended measure of CPU, memory, and I/O performance. The vCore model allows you to choose the number of virtual cores, memory, and storage independently, providing more flexibility and transparency in performance.

Intermediate Level

6. What are some security features available in Azure SQL Database?
   • Answer: Security features include:
     • Azure Active Directory Authentication: Centralized identity management.
     • Transparent Data Encryption (TDE): Encrypts data at rest.
     • Always Encrypted: Protects sensitive data during storage and processing.
     • SQL Firewall: Restricts access to the database based on IP addresses.
     • Advanced Threat Protection: Alerts about suspicious activities.
7. How can you scale an Azure SQL Database?
   • Answer: Scaling can be done either by:
     • Vertical Scaling: Changing the service tier or increasing DTUs/vCores.
     • Horizontal Scaling: Using Elastic Pools or sharding to distribute data across multiple databases.
8. What is a Managed Instance in Azure SQL Database?
   • Answer: A Managed Instance is a managed SQL Server instance in Azure that provides near-complete compatibility with on-premises SQL Server features, including support for SQL Server Agent, cross-database queries, and linked servers.
9. How do you perform a point-in-time restore in Azure SQL Database?
   • Answer: You can restore an Azure SQL Database to any point in time within the retention period by using the Azure portal, PowerShell, or Azure CLI. This is done by selecting the desired time during the restore process.
10. What is geo-replication in Azure SQL Database?
    • Answer: Geo-replication allows you to create readable secondary replicas of your database in different geographic regions for disaster recovery and load balancing. In case of a primary region failure, you can failover to a secondary replica.

Advanced Level

11. What are Hyperscale and Serverless tiers in Azure SQL Database?
    • Answer:
      • Hyperscale: Designed for databases with high scalability needs. It uses a distributed architecture that allows it to scale out storage and compute resources independently.
      • Serverless: Automatically scales compute resources based on workload demand and pauses during inactivity to save costs.
12. Explain how you would monitor performance in Azure SQL Database.
    • Answer: Performance can be monitored using tools like:
      • Azure Monitor: For metrics and alerts.
      • SQL Analytics in Azure Log Analytics: For query performance insights.
      • Query Store: Captures query performance data.
      • Dynamic Management Views (DMVs): For real-time monitoring of server state.
13. How does automatic tuning work in Azure SQL Database?
    • Answer: Automatic tuning helps optimize the performance of your database by automatically applying tuning recommendations, such as creating or dropping indexes and forcing plan changes based on workload patterns.
14. What is Data Sync in Azure SQL Database?
    • Answer: Data Sync is a service that allows you to synchronize data between Azure SQL databases and on-premises SQL databases. It can be used for hybrid cloud scenarios or to keep multiple databases synchronized.
15. How would you implement a disaster recovery plan using Azure SQL Database?
    • Answer: A disaster recovery plan can be implemented by:
      • Setting up Geo-Replication: To create replicas in different regions.
      • Using Azure Site Recovery: For broader disaster recovery that includes SQL databases as part of a larger application.
      • Regular Backups: Ensure regular and automated backups are configured.
      • Failover Groups: Automatically failover between primary and secondary databases during outages.
16. What are the differences between Azure SQL Database and SQL Server on an Azure VM?
    • Answer: Azure SQL Database is a fully managed PaaS offering with built-in high availability, automated backups, and scaling. SQL Server on an Azure VM (IaaS) requires manual management of the operating system, backups, and high availability configuration, but it provides full control over the SQL Server instance and the underlying OS.
17. How do you migrate an on-premises SQL Server database to Azure SQL Database?
    • Answer: Migration can be done using tools like:
      • Azure Database Migration Service (DMS): For comprehensive migration.
      • Data Migration Assistant (DMA): To assess and migrate databases.
      • BACPAC files: Exporting and importing databases.
18. What is Advanced Data Security in Azure SQL Database?
    • Answer: Advanced Data Security is a unified security package that includes Data Discovery and Classification, Vulnerability Assessment, and Advanced Threat Protection for proactive and real-time threat detection and response.
19. How can you optimize the cost of Azure SQL Database?
    • Answer: Cost optimization can be achieved by:
      • Choosing the right pricing tier (DTU vs. vCore).
      • Using Serverless tier for unpredictable workloads.
      • Leveraging Azure Hybrid Benefit if you have SQL Server licenses.
      • Elastic Pools to share resources among multiple databases.
20. What are the key differences between a Managed Instance and Single Database deployment model?
    • Answer:
      • Managed Instance provides near 100% compatibility with on-premises SQL Server features, including support for SQL Agent, linked servers, and cross-database queries.
      • Single Database is more isolated, with its resources dedicated to a single database, and lacks some of the advanced SQL Server features that Managed Instance supports.

cenario-based questions are designed to evaluate your practical knowledge and problem-solving abilities in real-world situations. Here are some scenario-based questions related to Azure SQL Server Database, along with possible approaches to answering them:

Scenario 1: Performance Issues

Question: You have received complaints that an Azure SQL Database is experiencing slow query performance during peak hours. How would you approach diagnosing and resolving this issue?

Answer:

1. Analyze Query Performance:
   • Use Query Store to identify long-running or resource-intensive queries.
   • Review Execution Plans to check for inefficiencies such as missing indexes or suboptimal query paths.
2. Monitor Resource Utilization:
   • Check CPU, memory, and I/O usage using Azure Monitor or Dynamic Management Views (DMVs).
   • Review DTU/vCore utilization to ensure the database is not under-provisioned.
3. Optimize Indexes:
   • Use Automatic Tuning to suggest and apply index optimizations.
   • Consider adding, modifying, or removing indexes based on query patterns.
4. Scale Resources:
   • If the database is consistently hitting resource limits, consider scaling up to a higher service tier or adding more vCores.
   • For highly variable workloads, consider using the Serverless tier to automatically scale during peak hours.
5. Review Database Design:
   • Ensure the database schema is optimized for the types of queries being executed.
   • Consider partitioning large tables to improve query performance.
6. Implement Caching:
   • Use Query Caching or Materialized Views for frequently accessed data.

Scenario 2: Disaster Recovery

Question: Your organization needs to implement a disaster recovery plan for an Azure SQL Database. The requirement is to have minimal data loss and quick failover to a secondary region in case of a regional outage. What solution would you recommend?

Answer:

1. Geo-Replication:
   • Set up Active Geo-Replication to create secondary replicas in different Azure regions.
   • Ensure the secondary databases are in readable mode for load balancing and can be promoted to the primary role in the event of a disaster.
2. Failover Strategy:
   • Define a Failover Policy for automatic or manual failover depending on business requirements.
   • Test failover regularly to ensure that the process is smooth and downtime is minimal.
3. Data Synchronization:
   • Ensure that data synchronization between primary and secondary replicas is in near real-time to minimize data loss.
4. Recovery Time Objective (RTO) and Recovery Point Objective (RPO):
   • Define RTO and RPO in your disaster recovery plan and ensure that the chosen solution meets these objectives.
   • RTO should focus on how quickly the system can be restored, and RPO on how much data loss is acceptable.
5. Monitoring and Alerts:
   • Implement monitoring and alerts for any issues with geo-replication or failover readiness.
   • Use Azure Site Recovery for broader disaster recovery planning if other resources are involved.
6. Documentation and Training:
   • Document the entire disaster recovery process and ensure the team is trained to execute it when necessary.

Scenario 3: Security Breach

Question: Your team suspects that there has been unauthorized access to the Azure SQL Database. What steps would you take to investigate and secure the database?

Answer:

1. Audit Logs Review:
   • Immediately review SQL Audit Logs and Azure Activity Logs to identify unauthorized access attempts, such as failed logins or unexpected data access.
2. Data Classification and Masking:
   • Verify if sensitive data has been accessed and ensure that Data Classification and Dynamic Data Masking are in place to limit exposure.
3. Threat Detection:
   • Use Advanced Threat Protection to review any alerts or anomalies that may indicate a security breach, such as SQL injection attempts or unusual data exfiltration.
4. Immediate Actions:
   • Restrict access by temporarily blocking suspicious IP addresses using the SQL Server Firewall.
   • Rotate credentials (passwords, keys) for users, applications, and services connected to the database.
5. Enhance Security Measures:
   • Enable Multi-Factor Authentication (MFA) for Azure AD users accessing the database.
   • Review and tighten Role-Based Access Control (RBAC) to ensure users only have access to what is necessary.
6. Patch and Update:
   • Ensure that all security patches are applied to both the database and the applications that access it.
7. Post-Incident Review:
   • Conduct a post-incident review to identify how the breach occurred and implement further controls to prevent future incidents.
   • Consider using Always Encrypted for sensitive data fields to protect data even if it’s accessed illegally.

Scenario 4: Cost Management

Question: The company’s Azure SQL Database costs have been increasing, and management has asked you to optimize the costs without compromising performance. What steps would you take?

Answer:

1. Evaluate Current Usage:
   • Analyze DTU/vCore utilization using Azure Monitor to see if the database is over-provisioned.
   • Review the billing reports to understand where costs are accumulating.
2. Right-Size the Database:
   • If the current performance tier is underutilized, consider scaling down to a lower DTU/vCore tier that matches your performance needs.
3. Use Elastic Pools:
   • If you have multiple databases with varying usage patterns, consider moving them to an Elastic Pool to share resources and reduce overall costs.
4. Leverage Serverless:
   • For databases with intermittent usage, switch to the Serverless tier, which automatically scales resources up and down based on demand and pauses during inactivity.
5. Optimize Storage:
   • Review the storage usage and consider archiving old data or using data compression techniques to reduce storage costs.
6. Azure Hybrid Benefit:
   • If you have existing SQL Server licenses, apply the Azure Hybrid Benefit to reduce the cost of the vCore-based model.
7. Optimize Query Performance:
   • Identify and optimize costly queries using Query Store to reduce the load on the database, potentially allowing for a lower tier.
8. Monitor and Alert:
   • Set up cost management alerts to notify you when spending exceeds certain thresholds.
9. Use Reserved Instances:
   • If your workload is predictable, consider purchasing reserved instances to get a significant discount compared to pay-as-you-go pricing.

Scenario 5: Migration to Azure

Question: Your organization is planning to migrate an on-premises SQL Server database to Azure SQL Database. What steps would you take to ensure a successful migration?

Answer:

1. Assessment:
   • Use the Data Migration Assistant (DMA) to assess the on-premises SQL Server database for compatibility issues and identify any features that might not be supported in Azure SQL Database.
2. Planning:
   • Choose the appropriate Azure SQL deployment model (Single Database, Managed Instance, or Elastic Pool) based on the application requirements.
   • Plan for downtime and communicate the migration window to stakeholders.
3. Pre-Migration Steps:
   • Optimize the on-premises database by removing unused indexes, fixing schema issues, and archiving old data to minimize the data transfer size.
   • Set up Azure Networking to ensure secure and efficient data transfer.
4. Migration:
   • Use the Azure Database Migration Service (DMS) for a streamlined migration process. This can be done online (minimal downtime) or offline (requires more downtime).
   • For smaller databases, consider exporting the database as a BACPAC file and importing it into Azure SQL Database.
5. Post-Migration Validation:
   • Validate the integrity and performance of the database after migration by running consistency checks (e.g., DBCC CHECKDB) and comparing query performance with on-premises benchmarks.
   • Update connection strings and other application configurations to point to the new Azure SQL Database.
6. Security and Compliance:
   • Apply security configurations, such as Transparent Data Encryption (TDE), firewall rules, and role-based access controls.
   • Ensure compliance with data governance policies by using Data Classification and Advanced Threat Protection.
7. Performance Tuning:
   • Monitor the database performance post-migration and make necessary adjustments, such as scaling resources or modifying indexes.
   • Implement Automatic Tuning to continuously optimize the database.
8. Documentation and Handover:
   • Document the entire migration process, including any issues encountered and resolutions.
   • Provide training or handover sessions to the operations team for ongoing management.