SQL interview questions

Whilst the demand for SQL candidates is strong, competition for jobs is also high. It’s therefore important to stand out against these other candidates at your interview and make a good first impression.

Whether you’ve been working in the database field for years, or are completely new to the industry, a key factor of interview success is preparation. Remember, you only have 30-60 minutes to make the interviewer see that you’re a perfect fit for the role. You therefore need to prepare by considering what SQL interview questions you could be asked and practice your answers. This can ensure you can get all the relevant information across, clearly and concisely.

Examples of SQL interview questions:

Whilst each SQL job will be different and every company will have a varied set of criteria for candidates, there are some key SQL interview questions that you will most probably get asked. Here are five typical SQL interview questions, along with some tips to help you answer them effectively:

1. How do you run a SQL query?

Your interviewer may start off by asking you relatively easy SQL interview questions, helping to ease you into the conversation and test your understanding of the fundamentals. Whilst it’s important to answer the question clearly and concisely, you can still demonstrate your broader knowledge.

Start by explaining that SQL (Structured Query Language) is a standard programming language that is used to access and manipulate data held in relational databases. To perform tasks, such as adding data and selecting fields, you need to run SQL queries. Queries are built using commands, with the six key SQL commands being “Select”, “Insert”, “Update”, “Delete”, “Create” and “Drop”. However, many SQL database systems have their own additional extensions. Next, explain how you run a SQL query, breaking down your answer into clear, distinguishable steps.

2. Describe the complexity of the ETL packages you have built

This SQL interview question is to help the interviewer know more about your experiences. However, it doesn’t mean you can’t demonstrate your knowledge at the same time.

Start by explaining what ETL (Extract, Transform and Load) is and what it does. In simple terms, it gets data from one database and puts it in another database. It therefore reads data from one database, converts the data into a compatible format before placing the data into the new database.

Next, discuss some of the ETL packages that you have built. Try to think of the most complex examples you can. Briefly explain how you built the packages and why, for example, were you converting the database into a different format, or creating a data warehouse? Don’t forget to explain the outcome too.

3. Explain how you would build a data warehouse from scratch

It’s simple to just list the steps you should theoretically take to build a data warehouse, but this won’t make you stand out from all the other job candidates. Therefore to answer this question, think of a time when you have built a data warehouse yourself from scratch. Then explain the steps you took. This not only helps to demonstrate your knowledge but also your experience.

A key part of building a data warehouse is extracting data from various data sources and putting them all in a central storage area. However, there’s much more involved in the process, so make sure you explain each step you would take, clearly and concisely.

4. What is the complexity of the SSRS reports you have built?

SQL Server Reporting Services (SSRS) is a solution by Microsoft that allows businesses to create, publish and manage reports for an SQL Server. Reports can be paginated so they’re easy to send via email, have a responsive layout so they’re easy to view from mobile devices, plus, you can also view reports on any web browser through a web portal.

The solution has been built so that even administrators with no SQL experience can create basic reports, using a simple report wizard. You’ll therefore have to think of some of the more complex SSRS reports you have created to really impress your interviewer. For example, as well as basic tables, have you created more complex data visualisations, with charts and maps? Have you also added KPIs and manually added parameters perhaps?

5. Tell me about a challenging SQL project you worked on

Interviewers like this question as it can tell them a lot about your personality and drive. Firstly, they want to know if you’ve ever been in a challenging situation, but most importantly, they want to know how you handled it. This is because it will help them to understand how you cope under pressure.

Make sure you think of a relevant example and draw positive conclusions from it that could relate to the role you’re currently applying for.

Of course, this isn’t an exhaustive list of questions you may be asked, but it’s a good starting point. By being prepared and familiarising yourself with these SQL interview questions and answers, you’ll have a much better chance of impressing your interviewer and securing your next job.

Want more examples of common job interview questions and answers? Take a look at our job interview tips hub for more interview tips and advice or search for current jobs.