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.

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.

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).

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."

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."

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."

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