Top 50 SQL Server Interview Questions With Example Answers
Updated 13 November 2022
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Developed by Microsoft, SQL Server is a database server based on the Relational Database Management System (RDBMS). Foundational to the infrastructure and business operations of many companies, it stores, manages, manipulates and retrieves information in databases. By reviewing the top interview questions on SQL Server, you can improve on your existing SQL Server knowledge and prepare well for your upcoming interview. In this article, we review some of the most frequently asked SQL Server interview questions and provide some example answers to help prepare for your interview.
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How Do I Prepare For An SQL Server Interview?
You can prepare for an SQL Server interview by rehearsing the answers for some of the most frequently asked SQL Server interview questions. Together with the targeted preparation, you can renew your knowledge of SQL basics such as basic queries, indexes, transactions and triggers. It can also help to research the company interviewing you and discover why it needs SQL Server and how it uses it to advance its business goals.
Related: What Is SQL? Definition and Benefits
What Are The Important Topics In SQL For An Interview?
The important topics in SQL for an interview may relate to the SQL database and its key structures. You may be required to explain the purpose and use of SQL databases, their structure and ways to manipulate the tables and data to get desired results. It can benefit you to master SQL concepts like SQL Commands, SQL Joins, SQL Constraints, Data Modelling, Select Queries, Relational Keys, Table Types, Data Definition Language (DDL) and Data Manipulation Language (DML).
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Top 44 SQL Server Interview Questions For Experienced Professionals
MS SQL Server questions generally include general and in-depth questions about your SQL Server experience and background. The interviewer may ask you questions based on your work experience. Here are some common questions based on your level of experience:
Questions for candidates with two years of SQL Server experience
You can review the following SQL Server questions for experienced professionals with at least two years in the field:
What is your understanding of SQL?
What do you know about RDBMS and DBMS?
What do you know about PL/SQL?
Can you give the differences between SQL and PL/SQL?
How would you create a database in the SQL Server?
What is the processing sequence of SQL statements?
What are the authentication modes in the SQL Server?
How do you execute a dynamic query?
What are the different Joins available in the SQL Server?
What do you know about a correlated subquery?
What do you know about user-defined data types?
What do you know about the OSQL utility?
How does OSQL differ from Query Analyser?
What do you know about the CHECK constraint?
What is a subquery, and what are its properties?
In SQL Server, what is COALESCE?
Can you explain triggers and list types of triggers?
Can you explain tables and fields?
Can you list the constraints in SQL?
How do clustered and non-clustered indexes differ?
Can you explain data integrity?
What is normalisation and denormalisation?
Related: A Comprehensive Guide To Different Types Of SQL Courses
Questions for candidates with five years of SQL Server experience
The following SQL Server questions for experienced professionals with at least five years in the field:
What is the difference between SQL Server and Postgre SQL?
What are a deadlock and a livelock?
In SQL, what are magic tables?
Can you explain aggregate and scalar functions?
What are the types of user-defined functions?
How can you create a user-defined function in the SQL Server?
What is the recovery model and give its types in the SQL Server?
What is a primary key and a unique key?
What are the different types of functions in the SQL Server?
What is an index, and why is it necessary in a database?
What are the benefits of replication in the SQL Server?
In SQL Server, what are the master data services?
What are some common performance issues in the SQL Server?
In SQL Server, what is a view?
How to delete a table from the SQL Server database?
What do you know about Online Transaction Processing (OLTP)?
Can you explain the purpose of the FLOOR function?
What is CheckPoint in the SQL Server?
What is an execution plan, and how can you view it?
What are local and global variables?
What do you know about subquery and its properties?
How are Integration Services useful in SQL Server?
Related: What Are the Different Database Types?
6 SQL Interview Questions With Sample Answers
Here are a few examples of additional SQL Server questions you might encounter in your interview with example responses to help you answer:
1. What is Data Warehousing?
This is a common question that interviewers often ask during SQL Server interviews. In your response, you can define data warehousing and provide a brief explanation of its purpose.
Example: "Data warehousing refers to digital data storage to secure information and create a resource depository of business and operational data. The company or organisation that undertakes the data warehousing can access, retrieve, update, analyse and manipulate the historical data. A data warehouse remains separate from operational databases and its key features are being subject-oriented, time-variant, integrated and non-volatile. Its purpose is to gather data from different sources, identify collection time period, retain all stored data and analyse it to make better business decisions."
Related: SQL Query Interview Questions for Freshers and Experienced Candidates (With Sample Answers)
2. Do you know the difference between DELETE and TRUNCATE commands?
The purpose of this common interview question is to test your understanding of SQL commands. You can explain what each command does and highlight their differences.
Example: "DELETE is a Data Manipulation Language (DML) command, and TRUNCATE is a Data Definition Language (DDL) command. With the DELETE command, you can remove one or more specified rows from a table. The TRUNCATE command removes all the rows.
You can use the DELETE command with the WHERE clause to delete only those rows that satisfy the condition. If you do not use the WHERE clause, the DELETE command would remove all the rows from the table. The TRUNCATE command does not have a WHERE clause. You can use DELETE with indexed views, which is not possible with TRUNCATE. After DELETE, you may perform Commit or Rollback. The Rollback option is not possible with TRUNCATE."
3. What are the advantages and disadvantages of stored procedures?
Interviewers may ask this to assess your technical knowledge of stored procedures. To answer this interview question, explain what a stored procedure is and give its advantages and disadvantages.
Example: "A stored procedure is a precompiled group of one or more T-SQL statements stored in the database. You only require to create them once and can call them multiple times when needed. The advantage of using stored procedures in SQL Server is that they are easy to maintain and reuse, reduce the load on the network and reduce execution time. It is possible to encrypt stored procedures to avoid SQL Injection attacks, and that improves data security. The disadvantage of stored procedures is that they are only executable in the database and take up a lot of memory."
4. What is TCL and which TCL Commands are available on the SQL Server?
Knowledge of TCL Commands is necessary for working with the SQL Server database, and interviewers may test you by asking this question. You can explain TCL Commands and list the available ones.
Example: "TCL stands for Transaction Control Language. TCL Commands are available on the SQL Server to manage transactions. There are three TCL Commands, and they are Commit, Rollback and Save Tran. With the Commit Command, you can save transactions permanently in the database. If you have made changes you do not want or want to return to the last committed state of the database, you can use the Rollback Command. With the Save Tran Command, you can save the transaction to a set savepoint. If you decide on a rollback later, the transaction can return to the savepoint location."
Related: Difference Between MySQL and SQL (With Definitions)
5. Can you explain Integration Services in SQL Server?
Many employers may require you to know or have experience with Integration Services in SQL Server, so expect this question in job interviews. You can define Integration Services and explain their use.
Example: "Integration Services is a specialised platform that makes use of graphical tools and wizards to build data migration, data integration and workflow applications. You can use its data warehousing tool to extract, transform and load data. With a service-oriented architecture (SOA), you can integrate applications."
6. What are the reporting services in SQL Server?
Experience with the SSRS may improve your career prospects, as it involves creating and sharing informative reports. In your interview answer, explain what SSRS is and its purpose.
Example: "The SQL Server Reporting Services (SSRS) is a server-based reporting platform from Microsoft. You can use the SSRS and its tools and services to prepare, deliver and manage printed and digitally interactive reports. You can design responsive layouts for the reports to enable them to adapt to different devices that your readers might use. With the SSRS, you can deliver the right information to the right people at the right time."
Related: SQL Career Skills (With Definition And Tips To Improve)
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