Looking to level up your SQL skills? Here's a list of the best platforms to practice SQL, ace your SQL interviews, and land your dream data role.
By Bala Priya C, KDnuggets Associate Editor & Technical Content Specialist on January 13, 2023 in SQL
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Have you ever been stumped by a SQL question in a data science interview? If so, you’re not alone.
All data roles across the board—data analyst, data scientist, data engineer, (insert your dream role here)—require proficiency in SQL. While SQL is an intuitive and easy language to learn, cracking SQL interviews is never easy. This is because acing SQL interviews requires much more than knowing your way around the syntax.
So how do you crack that interview? Is there a secret key? Well, deliberate practice is the key to mastering SQL. And in this guide, we’ll go over a list of practice platforms you can use to level up your SQL skills.
Let’s dive right in!
From software engineering to data analytics, HackerRank is one of the best platforms for practicing coding interview questions. HackerRank’s SQL practice suite has hundreds of questions available for you to practice.
You can filter the questions by their difficulty levels: easy, medium, and hard. Alternatively, depending on your comfort level, you can choose to practice questions on basic, intermediate, and advanced SQL topics. In addition, you can filter the practice questions by topics, such as select queries, joins, and aggregations.
After practicing, you can also take HackerRank’s Skills Certification Test to test your SQL skills. These tests are timed assessments that require you to solve SQL questions within a time limit. Currently, the following SQL assessments are available:
- SQL Basic tests you on simple queries, relationships, and aggregations.
- SQL Intermediate covers joins, unions, and subqueries.
- SQL Advanced includes query optimization, modeling, indexing, and window functions.
You can access the whole collection of practice questions and assessments with a free account on the platform.
SQLPad offers practice questions in the following broad areas:
- Single-table operations such as simple SELECT queries, using the WHERE clause, and GROUPBY
- Multi-table operations such as JOINs and UNIONs
- Window functions
For each of the above categories, there are questions with varying difficulty levels. They also offer SQL coding questions by the industry, such as fintech, education, and e-Commerce. With a free account, you can access some of the questions.
StrataScratch, another popular practice platform for SQL interviews, has a huge collection of SQL interview questions. In addition to filtering by topics and difficulty level, you can filter through the list of the questions to get company-specific SQL interview questions.
Their coding workspace supports PostgreSQL, MySQL, and Microsoft SQL Server (in beta). If Python is your preferred programming language, you can use pandas to solve the questions.
Under the free tier, you can access up to 50 questions with solutions, and attempt over 500 SQL questions.
DataLemur has a curated collection of SQL interview questions that have appeared in interviews in tech companies like LinkedIn, Tesla, Microsoft, and Walmart among others.
The platform has over 40 SQL interview questions on topics such as conditional aggregation, string and window functions, and cumulative sums.
If you are a Leetcode user, you can practice SQL on it too. The collection of SQL questions on LeetCode is quite diverse, with varying difficulty levels and topics. You can also filter questions by the tag: the tags correspond to the names of the companies. However, you can access only a subset of the questions with a free account.
If you are looking for a SQL learning platform where you can practice as you learn, then Mode can be a great choice. The Mode SQL tutorial has one of the most comprehensive and thoughtfully structured curriculum.
The Mode SQL tutorial into is divided into the following sections:
- Basic SQL
- Intermediate SQL covering joins, unions, and aggregate functions
- Advanced SQL covering topics like SQL subqueries, string functions, window functions, and pivoting
Each lesson has several practice questions that you can solve in the Mode SQL editor.
SQLZoo is another learning and practice platform for SQL. On SQLZoo, you can access bite-sized lessons to learn SQL: from basic SELECT statements to more advanced concepts like window functions. There are short practice exercises embedded into each of the lessons. To put your SQL skills to test, there’s a dedicated assessment section that has more involved SQL questions.
I hope you found this list of SQL practice platforms helpful. If you are starting out, you can try one or more of these platforms to find the right fit.
Choosing the right platform would also require you to factor in how much you already know and the bandwidth you have to practice. If you’re actively interviewing, it's always a good idea to double down on interview questions and refresh some tricky concepts like window functions, subqueries, and common table expressions. Here is a SQL cheat sheet you can bookmark for quick reference. Keep coding!
Bala Priya is a technical writer who enjoys creating long-form content. Her areas of interest include math, programming, and data science. She shares her learning with the developer community by authoring tutorials, how-to guides, and more.
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