53 Essential SQL Interview Questions to Know

If you have an upcoming interview and are facing SQL interview questions, you’ll definitely want to put in the time and effort to practice beforehand. But don’t let the idea of prep work overwhelm you. 

We’ll explain everything you need to know about answering SQL interview questions, including tips to ace the interview, the best ways to prepare, and 53 essential questions to practice before the interview. 

Best Ways to Prepare for SQL Interview Questions

There are lots of great ways to prepare for answering SQL interview questions, from brushing up on your fundamental knowledge to practicing questions out loud. 

Here are the best ways you can prepare for your upcoming interview, especially when it comes to acing the SQL interview questions. 

1. Make sure you have a strong SQL foundation to build off of.

To successfully answer SQL interview questions, you need to have a very strong foundation to begin with. Even if you feel confident, pencil in some time to review and strengthen your understanding as a whole.

While the core concepts are important, make sure you also consider the more advanced concepts, including: 

• Transactions
• Indexing
• Window functions
• Views
• Common table expressions (CTEs)

Strengthening your foundation also includes practicing problems, which we’ll delve into below.

2. Be sure to have a thorough understanding of SQL syntax and concepts.

Understanding SQL syntax and concepts are central to your success answering SQL interview questions. 

For example, you should be familiar and comfortable with basic concepts such as: 

• Subqueries, specifically how to nest queries within others
• Data query language (DQL), and how to use JOIN operations to combine data from multiple tables
• Data manipulation language (DML), and DML statements like INSERT, DELETE, UPDATE, and SELECT 
• Aggregate functions, particularly COUNT, MIN, MAX, AVG, and SUM 
• Data definition language (DDL), specifically how to use DDL statements like DROP TABLE, CREATE TABLE, and ALTER TABLE to manipulate tables
• Data types and operators, and how to use them

3. Practice solving problems with SQL.

Solving problems and SQL go hand-in-hand, so it’s no surprise that practicing these problems is an excellent way to prep. 

Before you start, remember the process to solving SQL problems: 

1. Pinpoint the problem and what the ideal output would be. 
2. Aim to break down the problem into smaller problems so you can solve it easier.
3. Based on your needs, choose the appropriate SQL commands. 
4. To make sure it’s correct, use test cases.
5. Finally, make your code more efficient through refactoring.

One way you can go about practicing problems is by using real-world datasets. This is a creative way to improve your problem-solving abilities with a variety of data. You could do this in many ways depending on your comfort level. For example, you could find some data analysis blogs to contribute to or check out a few open-source projects to get involved with. You could even volunteer with a non-profit and lend your skills to their cause if you’re comfortable. 

Of course, you can also practice straight from the comfort of your own home with some practice problems. Take advantage of online resources that offer SQL practice problems. For example, there are sites like SQLZoo and HackerRank that can provide challenges to tackle, along with explanations.

4. Practice answering SQL interview questions.

Nothing beats practicing SQL interview questions out loud. It should definitely be a priority for you if you have an interview coming up soon. 

Although you can always practice answering questions in front of a mirror, using a virtual interview simulation like Yoodli takes it a step further. Unlike a mirror, Yoodli gives you individualized feedback based on your speech and speaking patterns. 

You can start by downloading the Yoodli app for your desktop. Yoodli analyzes your speech to provide a whole host of data to paint a clearer picture of where you’re at in terms of interview prep. For example, it can tell you how many filler words you use and when, if you’re using inclusive language, and how fast you’re speaking, among other insights. 

Find out more about how it works by watching our overview explainer video:

To make the interview as realistic as possible, Yoodli uses generative AI technology to keep you on your toes with comprehensive follow-up questions. You can choose pre-existing questions to respond to from Yoodli’s question bank or you can input some of your own questions to practice, like SQL interview questions.

You can even personalize the interview to make the simulation more serious, friendly, or focused on behavioral questions. 

After you respond to the SQL interview questions, Yoodli will provide actual personalized feedback to help you improve. It might suggest you tighten up your language in areas to keep the response concise or maybe use less filler words. 

In terms of interview prep, there’s nothing that compares to practicing some common SQL interview questions out loud. 

53 Essential SQL Interview Questions

The more prepared you are for an interview, the more confident you’ll be going into it. As mentioned above, the best way to prepare, hands down, is by practicing answering questions out loud. 

Here are 53 essential SQL interview questions to practice before your interview:

1. What’s the difference between a view and a table?
2. What are your career goals?
3. List and explain the different data types in SQL.
4. Explain the difference between implicit and explicit conversions in plain language.
5. Describe your approach to debugging SQL queries.
6. What is a foreign key?
7. What’s your experience with using SQL in a real-world setting and practical applications?
8. Walk me through how you handle NULL values in SQL?
9. Explain the differences between DDL, DML, and DQL.
10. Describe the various types of joins in SQL and when you’d use them.
11. What is your least favorite SQL feature and why?
12. What is an aggregate function?
13. Why are you interested in a career in SQL?
14. What are self-joins?
15. Write a query to select all the customers from a table named “customers” who live in Georgia.
16. Explain what an OLAP (Online Analytical Processing) system is.
17. Write a query to delete all the orders from the “orders” table that were placed before 2021-01-01.
18. List the different ways to sort data in SQL.
19. How would you describe denormalization?
20. Write a query to find the customer with the most orders in the “orders” table.
21. What is a stored procedure?
22. If you wanted to filter data using WHERE clauses and other conditions, how would you do so? 
23. What is a CTE (Common Table Expression)?
24. What is an index?
25. Explain what a trigger is.
26. List the various types of aggregate functions and how you’d use them.
27. What is a window function?
28. How would you describe normalization?
29. Write a query to find the average cost of all the products in the “products” table.
30. Explain what window functions are and why they’re used.
31. What is an OLTP (Online Transaction Processing) system?
32. Write a query to update the “cost” column in the “products” table by 30%.
33. What is a data warehouse?
34. List the various types of subqueries. How would you use each one?
35. What is a join?
36. What is your favorite SQL feature and why?
37. How would you explain what a subquery is?
38. With SQL queries, how would you go about debugging and troubleshooting them?
39. How do you stay up-to-date on the latest SQL trends?
40. Explain what a relational database is.
41. How do you deal with complicated SQL problems?
42. Describe the different types of indexes.
43. What is a primary key?
44. Tell me how you work with other developers to solve SQL problems.
45. What are the different operators in SQL?
46. How do you handle transactions?
47. Why are you interested in working for this company and what can you bring to the table?
48. Tell me about what you know about this company’s data architecture and how we use SQL here.
49. Let’s say you want to secure a database from unauthorized access. How would you go about it?
50. Describe the various types of data visualization methods.
51. Tell me how you use SQL to create dashboards and reports. 
52. In the field of SQL, what are your professional goals?
53. How do you deal with working with a significant amount of data?

Tips for the SQL Interview

Though you might feel nervous for your upcoming interview, especially when it comes to answering SQL questions, try not to let your anxiety get the best of you. 

Here are a few tips to ace the interview (and the questions that come with it). 

Use the STAR method to answer SQL interview questions

One underrated tip is learning to use the STAR method to best answer SQL interview questions. The acronym stands for situation, task, action, and result. 

So to use this method in your interview responses, start by explaining the situation, including context, in terms of your prior work or projects. Next, explain the task or your role in the project or situation. Afterward, you can describe the actions you took to successfully complete your part of the project. 

Finally, you can take a dive into the results of your project. This is a great place to include your specific contributions and skills that led to the success (and relate them back to the position’s job requirements). 

Show you’re passionate and excited about SQL

Many candidates don’t realize how important being enthusiastic about SQL is in an interview. It’s essential to show you’re passionate and excited when answering SQL questions so that the interview knows you’re interested and a good fit for the position. 

To show your passion for SQL, you can do things like:

• Explain how you first started with SQL and why
• Emphasize why data interests you
• Mention how the practical applications of SQL excites you
• Explicitly mention your eagerness to learn more

You can also show your excitement by asking interview questions for interviewers and other specific queries toward the end of the interview. 

Know the position and its responsibilities well

One of the best tips for any interview is to study the job description and its responsibilities well so that you can relate any of your experience back to the specific qualifications the interviewer is looking for. 

Make sure you know the job requirements in and out, and practice connecting your prior work experience to the skills and qualifications for the position you’re interviewing for. This will make it so much easier during your actual interview so you don’t have to feel like you’re scrambling or grasping at straws. 

Practice explaining your SQL solutions

Explaining SQL solutions isn’t as easy as it seems, even if you’re explaining your own solutions. Knowing how to express and explain the logic behind your SQL solutions is a skill in and of itself. 

To practice, tackle some problems and write down your explanation as to how you solved it. Explain your approach without any jargon or technical language. You should be able to explain SQL solutions to someone without any prior knowledge. For example, you could practice running through your solution to a friend or family member. 

Sometimes, using visuals can help explain your solutions too. For example, you could use notes or diagrams to conceptualize the work you did and make it easier for someone to understand. 

It might also be insightful to record yourself while you try to explain, so that you can go back and review your response and identify areas it could be improved. A communication coach like Yoodli is perfect for analyzing recorded responses (more on that below). 

The Key Takeaway 

Once you’ve put in the time and effort to practice, you’re ready to ace those SQL interview questions. Be confident and try to channel any anxiety into excitement. 

An interview like this is always exhilarating, and practicing with a communication technology tool like Yoodli is a great way to set you apart from the crowd. 

Sources

• Khan Academy: “Unit 3: Intro to SQL: Querying and managing data.”
• Code Academy: “Learn SQL.”
• Geeks for Geeks: “SQL Tutorial.” 
• HackerRank: “Solve SQL.”
• Indeed: “10 Uses of SQL (With Definition, Benefits and Examples).”