Top SQL Server Interview Questions And Answer

Microsoft SQL Server has shown a notable popularity as a relational database management system (RDBMS) with its capability to store and retrieve data from various software applications. It has grabbed the attention of various companies and they are in a quick search for SQL Server professionals. I am here with a comprehensive overview of most asked SQL Server interview questions and answers for job hunters, hiring managers and recruiters.

This SQL server interview preparation guide explores SQL questions and answers for beginners, intermediate and experienced practitioners. It will help you to know what to expect and what to check in interviews. By the end, you will be all set to showcase your SQL Server skills and grab the opportunity.

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SQL Server Interview Questions and Answers

The first thing we have to consider in an interview preparation is to understand the requirements of the targeted job. There are a variety of job roles available depending on different experience and expertise levels. Therefore, we have designed this article to cater to each kind of job role requirements. Let's start.

Basic SQL Server Interview Questions

A beginner is the first step to start a career in this field. It requires knowledge of fundamentals like SQL, statements or commands, dialects, entities, etc. Here in this section, we will discuss the frequently asked SQL Server interview questions for beginners.

1. What is SQL?

SQL (Structured Query Language) dialects are the different versions of this language. All these versions are very similar in terms of syntax and different in terms of functionalities. Some instances of these dialects are Microsoft SQL Server, MySQL, SQLite, PostgreSQL, Oracle, T-SQL, etc..

2. What do you understand about SQL dialects? Give some instances.

SQL dialects are the different versions of this language. All these versions are very similar in terms of their syntax and different in terms of functionalities. Some instances of these dialects are Microsoft SQL Server, MySQL, SQLite, PostgreSQL, Oracle, T-SQL and MongoDB.

3. What are SQL statements?

SQL statements are the commands interpreted via SQL engines to execute different data operations. There are many commands available in this language to manipulate information according to needs. Here are some their types with instances -

• Data Definition Language (DDL) - This command is used for modifying and defining the structure of a database. It includes TABLE, DROP, CREATE, TRUNCATE, ALTER, etc.

• Data Manipulation Language (DML) - It is a command of accessing, manipulating and modifying information from data stores. It includes INSERT, DELETE and UPDATE.

• Data Control Language (DCL) - This command is used for controlling user access to the information of databases and giving or revoking privileges to a particular or a group of individuals. It includes GRANT and REVOKE.

• Transaction Control Language (TCL) - This command is specially used in transactions. It includes SET TRANSACTION, COMMIT, SAVEPOINT and ROLLBACK.

• Data Query Language (DQL) - This command is used in performing queries in data banks for retrieving the necessary information. It includes SELECT.

4. What is normalization?

Normalization is a method of organizing information to minimize redundancy and improve logical integrity. Here, databases are divided into two or more tables to determine a relationship between them. This technique works as a performance booster for databases. 1NF, 2NF, 3NF, BCNF, 4NF and 5NF are some common normalization techniques of this database management system.

5. What are entities in data banks?

Entities represent real-world objects or concepts that can be stored in a database, like a customer or product. Each entity corresponds to a table, and each row represents a single instance of the entity.

Related Article- What is PL/SQL- Everything You Need To Know

SQL Server Interview Questions for Begginers

After completing more than 4 years of experience in this field, one may want to improve their career. It requires knowledge of advanced concepts like collation sensitivity, standby servers, statements, etc. Here are frequently asked SQL Server interview questions for intermediates, suitable for their career improvement.

6. What do you understand by collation sensitivity? Explain their types.

Collation sensitivity defines the rules for data character string sorting and comparison. After selecting the collation for the server, database or any column, a certain characteristic will be applied to that information. It will arrange all the information according to the applied rule. These rules include correct character sequence, character width, case sensitivity, accent marks, etc. Here are some commonly used collation sensitivities -

• Accent sensitivity

• Case sensitivity

• Width sensitivity

• Kana sensitivity

7. What is a standby server in SQL Server?

A standby server is a replacement of an available server of a DBMS. For instance, an application is running on the main server and due to some issue, the server goes offline. Here, the app will stop running in the absence of a server. It requires an additional server to run properly without any disturbance.

This additional server is known as the standby server and is very important for the DBMS. This DBMS server has three types of additional servers, including hot standby, warm standby and cold standby.

8. How do you differentiate between clustered and non-clustered indexes?

Both of these are types of indexes available on SQL DBMS that have different functionalities. Here are some of their differences -

• Clustered Index - This index changes the way records are physically stored in a table. It results in an exact sequence in which data was physically stored. A table cannot have more than one clustered index. It is often created by primary key constants with an index id of zero. It contains data pages in the leaf nodes.

• Non-clustered Index - In this index, the logical order of stored data does not match with physical order of data on disk. Here, both information and indexes are stored in different spaces. The leaf nodes of this index contain rows instead of datapages. Its index id is greater than zero.

9. What is the procedure for inserting, deleting and updating information from a table?

These three operations are performed with different statements (commands) as given below -

• Insert (INSERT INTO statement)

• Update (UPDATE statement)

• Delete (DELETE FROM statement)

10. How to build a stored procedure and grant permission to users on SQL Server?

Creating a stored procedure and giving access to users are two different processes. Stored permission is created by the CREATE PROCEDURE statement. Given below is an instance of this process -

The GRANT statement is used for granting permissions to users. These permissions are given on different levels like schema, data store, table and many more. Given below is an instance of this statement -

SQL Server Interview Questions For DBA

Let's come to role based interview questions. Here are some commonly asked SQL DBA interview questions and answers. These questions consist of the knowledge required to become a SQL database administrator. Explore this information to start your career in database management with SQL.

11. What authentication modes does SQL Server support?

This DBMS has two types of authentication modes including mixed mode and windows authentication. Windows authentication is a default mode or integrated security of this system. It only trusts the window users and groups accounts for logging in the server.

Mixed mode is an additional security for some special instances. It is often used for legacy purposes and compatibility with older apps. It is enabled in case the database has to be connected with third parties by force. With this mode, only trusted users are enabled to interact with systems.

12. How to conceal an SQL server instance?

It is concealed with a step-by-step procedure. This process includes opening Configuration Manager> expanding network configuration > clicking right on protocol for server instance > selecting properties > navigating flags tab > selecting yes from hide instance option > saving the changes. The port number should be given to the connection string for establishing a connection.

13. What are the differences between SQL Server and Oracle?

Both these servers are different in terms of complexity and functionality. SQL Server is easy to learn as it uses T-SQL language with straightforward syntax. It only runs on two platforms including Linux and Windows.

Oracle is comparatively complicated to learn as it uses PL/SQL language with intricate syntax. Despite its complexity, it gives more advanced functionalities. This server runs on different platforms like Windows, Linux, Solaris and Unix.

14. What do you understand about PHYSICAL_ONLY?

PHYSICAL_ONLY is a command in DBCC CHECKDB for restricting checks to the integrity of the physical structure of the page and record headers. It detects checksum failures, torn pages and common hardware failures. This operation minimizes the runtime for DBCC CHECKDB on big databases and is suggested for frequent use.

15. How to check data purity with DBCC CHECKDB?

DBCC CHECKDB has a command for checking the column values that are not valid for out of range. This command visualizes columns with date and time values that are either gigantic or smaller than the DATETIME datatype. It also restricts evaluating the physical integrity of the page and records. The command is -

Related Article - PostgreSQL Tutorial For Beginners

SQL Server Interview Questions on Integration Services

Some job roles like developers require knowledge in SSIS (SQL Server Integration Services). These developers get huge salary packages up to $130,496 per annum. Here are some frequently asked questions on integration services that will prepare you for the interview.

16. List the components of SSIS.

Listed below are the components of SSIS -

• Data Flow Elements

• Control Flow Elements

• Integration Services Projects

• Integration Services Variables

• Integration Services Packages

• Integration Services Connections

• Integration Services Log Providers

• Integration Services Event Handlers

17. What are the elements (tabs) in the default package designer of BIDS?

There are four elements including data flow, control flow, package explorer and event handler available in default package designer of BIDS.

18. What is a task in SSIS?

Task defines a special action or activity to perform a part of a package. It is a fundamental building block of package workflows. Each task performs a particular activity including data extraction, data conversion and data loading.

19. What is data flow and control flow?

Both of these are elements of SSIS. Control flow performs functions, gives structure and controls the flow of elements. The workflow in SSIS is called control flow. There should be at least one control flow in an SSIS package. It links modular data-flows together as a series of tasks for achieving a required result.

Data flow elements perform the ETL related tasks. This element is not necessary to have in SSIS. It has destinations and sources which extract and load information, transformations which customize and extend information, and paths which link transformations, sources and destinations. It has to be included to add a data flow to a package.

20. Explain the SSIS functionality in the management studio.

Following are the functionalities of this service in management studio -

• Observe the SSIS log.

• Delete & run packages.

• Export or import packages.

• Login in the SSIS instance.

• Observe the packages in a real time instance.

• Browse the packages from MSDB or file system.

Related Article- MongoDB vs MySQL - A Complete Comparative Guide

SQL Server Interview Questions on Reporting Services

Most companies require some additional skills in SSRS (SQL server reporting services) alongside the SQL. This section consists of the most asked and important questions on reporting services. Go through this section to understand what types of questions may be asked and how to answer them.

21. What is SSRS?

SQL server reporting services is a server platform with detailed reporting features for different data sources. This platform comprises a complete set of tools. These tools manage, build and give reports and APIs for coordinating data and reporting processes in custom apps.

22. What are the fundamental components of SSRS?

The fundamental components of this server based platform are -

• Data Sources

• Report Server

• Report Manager

• Report Designer

• Report Server Database

• Report Server & Command line utilities

• Browser types supported by reporting services

23. How to create a report on SSRS?

Creating reports on this platform includes developing a data source > creating one or more datasets as per source requirements> adding required control from toolbox > formatting the controls > verifying and validating reports > deploying the report.

24. How many types of reports are created on SSRS?

Many types of reports are created on this platform including snapshot, parameterized, click through, drill through, drill down, ad-hoc, cached, linked and subreports.

25. How to build a calendar parameter in an SSRS report?

Calendar parameter is created with the following steps -

• Create a parameter giving it a name like CalanderDate.

• Define data type of parameter as Date.

• Select None from the Available Values section.

• Select Today from the Default Value section.

Related Article - What is PostgreSQL and What It Is Used For?

SQL Server Interview Questions For Intermediate

Let's come to the most experienced SQL interview questions. It gives a deep understanding in performance optimization strategies, complex queries and server administration tasks. Exploring these questions will elevent one's skills to the next level.

26. What will be your approach to change or manage replication from an SQL server?

Managing or configuring replication from an SQL server is a multi step process. It involves identifying distributor and publisher > selecting type of replication from transactional, merge and snapshot > built publication to specify data > define subscription for delivering replicated information > monitor the performance of replication with replication monitor or SSMS > manage maintenance tasks like backup, restoration or index maintenance.

27. Write a script for importing information from a flat file into a table on SQL server.

BULK INSERT statement is apt for importing information from a flat file into a table. In this statement, we have to give the name of the table, let's take it as annual expenses. Then give the path to a flat file like 'C:\Path\To\Your\File.csv' and adjust ROWTERMINATOR and FIELDTERMINATOR as per requirements.

28. Develop a query to view odd values in tables.

29. Develop a query to view a non-equi join.

Non-equi join is a method of combining two joins with different conditions. Here operators like <, >, <>, != and BETWEEN are used.

30. Write a query to build a VIEW.

Advanced SQL Server Interview Questions

Let's discuss some advanced interview questions that may be asked by interviewers. These questions revolve around some advanced topics of this DBMS. Exploring these questions will improve your knowledge and sharpen your skills. Go through this section and become capable of joining a Silicon Valley company with a high-position job role.

31. What is an ALIAS?

ALIAS is a name given to a table WHERE statement. This name works as the identity of that table. The main reason for using ALIAS is to improve the readability of column names. It is built with the AS keyword and only exists alongside the query.

• Alias Syntax for column -

• Alias syntax for table -

32. How to update a table?

This is how a table is updated in SQL -

33. What are the components of SSIS packages?

The components of SSIS packages are -

• Data flow - The primary component of SSIS packages is data flow. It is responsible for transferring the information from one space to another within a dataset. Source, transformation and destination are the three main parts of this component.

• Control flow - Control Flow is another component of SSIS packages. It is responsible for defining the order and execution of operations. Tasks like conditional execution, looping, SQL and script execution and managing workloads come under this component.

• Package Explorer - The Package Explorer of SSIS navigates and manages package components. It displays the hierarchy from the package, including data flow components, control flow tasks, variables, connection managers and event handlers.

• Event handler - Event Handler is responsible for the package reacting to certain events in a process. These events are errors, package start, package end, warnings, task completion, etc. These components are apt for custom error handling, notifications, logging and many more actions during package execution.

34. Can you write an SQL query to detect the nth highest salary from a given employee table?

The query given below can find the nth highest salary from a given employee table.

35. Develop an SQL query that calculates the number of products sold in every month.

Scenario-Based SQL Server Interview Questions

Now we will explore the most asked Scenario-Based SQL Server Interview Questions and answers. These are mostly asked to highly experienced professionals, going for senior job roles.

Scenario-Based SQL Server Interview Questions

Now we will explore the most asked Scenario-Based SQL Server Interview Questions and answers. These are mostly asked to highly experienced professionals, going for senior job roles.

36. Have you ever faced a scenario where you deployed a new feature and one of the SQL queries suddenly became slow. How would you diagnose and fix it?

I have faced this type of issue. A query that previously executed in 200 ms has incred the processing time up to 8 to 10 seconds. To diagnose it I followed the given strategy:

• Check Execution Plan – Look for scans instead of seeks, missing indexes, key lookups, or expensive sort/hash operations.

• Check Parameter Sniffing – Sometimes SQL Server stores a plan based on an unusual parameter.
• Fix: OPTIMIZE FOR hint, RECOMPILE, or updating statistics.

• Check Index Fragmentation or Missing Index – If an index has 60% fragmentation, rebuild/reorganize it.

• Look at Blocking – Use sp_whoisactive or Activity Monitor to identify blocking chains.

• Review Changes – If a recent schema or statistics change happened, update statistics or revert poor indexes.

Final Fix: The slow query had a missing index after the code change. So, I have added a non-clustered index on the filtered column. It reduced execution time from 8 seconds to 250 ms.

37. Describe a scenario where your SQL Server CPU usage suddenly spiked to 90–100%. How did you identify the root cause?

One morning, my CPU hit 100% and the application became slow. Then, I followed the given strategy to fix it:

1. Check top CPU-consuming queries:

SELECT TOP 10 total_worker_time, execution_count, query_hash, query_plan 
FROM sys.dm_exec_query_stats 
ORDER BY total_worker_time DESC;

2. Found a query performing multiple table scans on a large table.

3. Stats were outdated; auto-update was disabled temporarily during maintenance.

Resolution:

UPDATE STATISTICS Sales WITH FULLSCAN;

Added a missing index to reduce scans.

38. Describe a scenario where your application frequently encounters SQL deadlocks. How did you resolve them?

There was a situation where multiple users were updating the Orders and Inventory tables simultaneously. It caused deadlocks because queries accessed the tables in different order. I used the following steps to fix it:

• Captured deadlock graph using Extended Events.

• Identified the conflicting queries.

• Standardized transaction order (Always update Orders table first, then Inventory.)

Additional fixes:

• Reduced transaction scope.

• Added appropriate indexes.

• Applied row-versioning by enabling READ_COMMITTED_SNAPSHOT.

39. Describe a scenario where a SQL Server log file kept growing uncontrollably. What steps did you take to handle it?

There was a situation where the log file grew from 5 GB to 60 GB overnight and filled the drive. It happened when database was in FULL recovery mode, but backups were not running for 2 days. I fixed it with the given steps:

1. Verified recovery model:

SELECT recovery_model_desc 
FROM sys.databases 
WHERE name='MyDB';

2. Took a transaction log backup to truncate inactive logs.

3. Identified a long-running open transaction using DMV queries.

4. After log backup, shrunk the log file:

DBCC SHRINKFILE (MyDB_log, 8000);

Best prevention: Scheduled regular log backups every 2 hours.

40. Describe a scenario where users reported missing records in the application while the records actually existed in SQL Server. How did you debug this?

There were a situation where multiple users complained that new orders were not visible on the dashboard. The reasons were:

• Records existed in the table, but the application query used NOLOCK, causing dirty reads.

• Another long transaction was blocking updates, leading to inconsistent results.

• Additionally, the dashboard query used a cached execution plan that was suboptimal.

Solution:

• Removed unnecessary NOLOCK.

• Fixed the blocking transaction.

EXEC sp_recompile 'GetDashboardOrders';

• After changes, the dashboard displayed correct data consistently.

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Wrapping Up

Well, in this guide we have listed top SQL server interview questions for different level job posts. It has included all the commonly asked topics from fundamentals to advanced level. It is suitable for both candidates and recruiters. Using this content alongside study sources will prepare candidates for their next interview. Recruiters may find out the best candidates for their company with this material.

FAQs

Q1. From where should I start to learn SQL?

Ans. Knowing where to start is essential to learn any technology like SQL. There are a variety of options out there like SQL tutorials, books, documentation and online courses. You just have to choose wisely.

Q2. How should I prepare for my next SQL server interview?

Ans. The SQL interview questions and answers mentioned in this article are best for preparing for this interview. You can also leverage some additional resources.

Q3. What are the 5 basic SQL commands?

Ans. The following are the 5 basic SQL commands one should know:

• DQL - Data Query Language.

• DCL - Data Control Language.

• DDL - Data Definition Language.

• DML - Data Manipulation Language.

• TCL - Transaction Control Language.

Q4. Is SQL Server easy to learn for beginners?

Yes, SQL Server is mainly easy to learn if you understand basic SQL concepts and practice regularly.