Interview Questions for SQL Server

If you’re preparing for an interview that includes SQL Server expertise, understanding the key concepts and practical knowledge of database management is essential. SQL Server is a complex and feature-rich platform, and interviewers often focus on a mix of technical and problem-solving questions. Below, we explore some common SQL Server interview topics and questions to help you prepare effectively.

1. Steps Involved in Upgrading SQL Server to a New Version

When upgrading SQL Server, it’s important to follow a structured approach:

Assess current compatibility and database features.
Perform a backup of all databases, including system databases.
Test the upgrade in a non-production environment.
Upgrade SQL Server using the setup wizard or command-line tools.
Validate the upgrade by testing applications and database performance.

Sample Question:
What are the key considerations when performing an in-place upgrade versus a side-by-side upgrade?

2. Managing Multiple SQL Server Instances

Managing multiple instances involves:

Configuring SQL Server Management Studio (SSMS) to connect to various servers.
Setting up Central Management Servers (CMS) for unified management.
Monitoring performance and resource allocation using tools like SQL Server Profiler and Extended Events.

Sample Question:
How would you implement Central Management Servers to efficiently manage multiple SQL Server instances?

3. Recovery Models

SQL Server offers three recovery models: Simple, Full, and Bulk-Logged. Each serves different use cases for managing transaction logs and backups.

Simple: Minimal log management, suitable for test or non-critical databases.
Full: Provides point-in-time recovery but requires log backups.
Bulk-Logged: Optimized for bulk operations while still allowing recovery.

Sample Question:
What recovery model would you choose for a highly transactional database and why?

4. Concept of Indexes

Indexes improve query performance by reducing data retrieval times. Common types include:

Clustered Indexes
Non-Clustered Indexes
Unique Indexes
Filtered Indexes

Sample Question:
Explain the difference between a clustered index and a non-clustered index, and provide a scenario where each is preferable.

5. Log Shipping

Log shipping is a disaster recovery solution involving:

Backing up transaction logs on the primary server.
Copying and restoring them to a secondary server.
Setting up a monitoring system for log shipping jobs.

Sample Question:
What are the advantages and limitations of log shipping compared to other disaster recovery options like Always On Availability Groups?

6. Query Optimization

Query optimization involves fine-tuning SQL queries to improve execution times and reduce resource consumption. Techniques include:

Analyzing execution plans.
Creating and maintaining indexes.
Avoiding unnecessary joins and subqueries.

Sample Question:
How would you identify and resolve performance bottlenecks in a slow-running query?

7. Deadlocks

Deadlocks occur when two processes block each other by holding a lock that the other process needs. Resolving deadlocks involves:

Using SQL Server Profiler or Extended Events to identify the cause.
Modifying transaction logic to minimize lock contention.
Using appropriate isolation levels and index strategies.

Sample Question:
Describe a time you resolved a deadlock in a production environment.

8. Normalization

Normalization structures databases to reduce redundancy and improve integrity. Common forms include:

First Normal Form (1NF): Eliminate duplicate columns.
Second Normal Form (2NF): Ensure all non-key attributes depend on the primary key.
Third Normal Form (3NF): Remove transitive dependencies.

Sample Question:
What are the benefits and potential drawbacks of over-normalization in a high-performance application?

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