Ask five people which SQL prep platform is best and you'll get five different answers, usually depending on which one they happened to try first. That's not very helpful when you've got an interview in three weeks and limited time to waste on the wrong tool.
This guide pulls together independent reviews, candidate feedback from forums like Blind and Reddit, and each platform's own documented features, to give you a straight answer: what each platform actually does well, where it falls short, and which one fits your specific situation. No single platform wins for everyone, so the goal here is matching, not crowning a winner.
Quick Answer: Which platform should you use?
If you're prepping specifically for data analyst or data scientist interviews, StrataScratch has the largest bank of real, company-sourced questions. If you want a completely free option with strong fundamentals coverage, LeetCode's database section is hard to beat. If you want curated, verified company-specific questions in smaller doses, DataLemur is a solid, focused choice. Most candidates get the best results combining two platforms rather than relying on just one.
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What Actually Matters When Choosing a Platform
Before ranking anything, it helps to be clear about what actually predicts whether a platform will help you. Question count alone is a weak signal, since a platform with 700 low-quality questions can teach you less than one with 50 well-chosen ones. The things that actually matter:
- Whether questions are sourced from real interviews, or just generic practice problems dressed up as interview prep
- Whether you can filter by company, role, or difficulty, so your practice time maps to your actual interview
- Whether the feedback loop teaches you something when you get a question wrong, rather than just marking it incorrect
- Whether the platform is built for data roles specifically, or adapted from a general software engineering tool
- How much of the useful content sits behind a paywall versus being genuinely accessible for free
The Platforms Compared
| Platform | Best for | Free tier | Weakness |
|---|---|---|---|
| StrataScratch | Data analyst and data scientist interviews specifically | Roughly 50 questions with solutions | Interface can feel cluttered and occasionally buggy |
| LeetCode (Database) | Drilling core SQL syntax for free, any tech role | Large, reliable free access to most SQL problems | Built for software engineers first; not data-role specific |
| DataLemur | Curated, verified company-specific questions | Roughly 30 to 50 questions | Smaller question bank; feedback is mostly self-check, not guided |
| HackerRank SQL | Structured skill certifications and broad practice | Solid free access | Less focused specifically on interview-style company questions |
StrataScratch
StrataScratch has become a go-to for data analyst and data scientist candidates specifically, largely because its question bank is sourced from real interviews at companies like Google, Amazon, and Meta, and you can filter directly by company. The coding workspace supports PostgreSQL, MySQL, and Microsoft SQL Server, and Python practice with pandas is available too if your interview loop covers both languages.
The tradeoff reviewers consistently mention is polish. Several independent reviews describe the interface as functional but not always smooth, with occasional loading issues on the question list. If a clean, bug-free interface matters a lot to you, weigh that against the strength of the question bank itself.
LeetCode (Database Section)
LeetCode wasn't built for data roles. It was built for software engineering interviews, and its database section is essentially a strong SQL syntax trainer bolted onto a much bigger platform. That said, its size and reliability make it hard to skip entirely. With roughly 250 SQL problems freely accessible, it's the most cost-effective way to drill fundamentals like joins, subqueries, and aggregate functions.
The catch: a large share of what LeetCode is best known for (algorithm-heavy coding challenges) is irrelevant if you're prepping specifically for a data analyst interview. Treat the database section as a standalone resource rather than expecting the rest of the platform to be relevant to your prep.
DataLemur
DataLemur takes a curation-first approach. Its question bank is smaller than StrataScratch's, but reviewers note the company-sourcing claims tend to be more consistently accurate, meaning when a question is labeled as having appeared in a specific company's interview, there's reasonable confidence that's true. It covers a solid range of topics, including window functions, conditional aggregation, and cumulative sums, which are exactly the areas that trip up a lot of intermediate candidates.
The main limitation reviewers point out is the feedback loop. When your query is wrong, DataLemur typically shows you the expected output and leaves you to compare it against your own result manually, rather than explaining exactly where your logic diverged.
HackerRank SQL
HackerRank leans toward structured, certifiable skill practice rather than curated interview-style questions. It's a reasonable free option for broad SQL practice and has the advantage of skill certificates some candidates use to strengthen a resume or LinkedIn profile. It's generally considered less focused than StrataScratch or DataLemur if your specific goal is interview-style, company-flavored practice.
Which One Fits Your Situation?
| Your situation | Recommended starting point |
|---|---|
| You're a complete SQL beginner | LeetCode's easier database problems, or a structured course, before jumping into interview-style questions |
| You're prepping specifically for a data analyst or data scientist role | StrataScratch, for the volume of role-relevant, company-sourced questions |
| You want free, reliable syntax drilling | LeetCode database section or HackerRank SQL |
| You want smaller, tightly curated, verified company questions | DataLemur |
| Your interview loop includes both SQL and Python | StrataScratch, since it supports both in one workspace |
| You have less than two weeks and need to prioritize ruthlessly | Pick one platform, focus on window functions, joins, and aggregations specifically, since these show up constantly |
Is It Worth Paying?
A determined candidate can genuinely get interview-ready using free tiers alone, especially by combining LeetCode's large free database section with StrataScratch or DataLemur's smaller free samples. What a paid subscription typically buys you is volume, company-specific filtering, and in some cases guided feedback or AI-assisted review when your query is wrong.
Whether that's worth the monthly cost depends mostly on your timeline. If you have two months and steady daily practice time, free tiers plus disciplined self-review can get you most of the way there. If you have two weeks and need to move fast, paying for one platform's full question bank is often the more efficient use of a short runway.
A Realistic Study Plan
| Week | Focus |
|---|---|
| 1 | Fundamentals: SELECT, WHERE, JOINs, GROUP BY. Use LeetCode or HackerRank's free problems daily. |
| 2 | Intermediate patterns: window functions, subqueries, CASE statements. Move to StrataScratch or DataLemur for company-flavored practice. |
| 3 | Timed, interview-style practice on your target company's question style, plus a review pass on every mistake from weeks 1 and 2. |
If window functions are still shaky heading into week 2, our guide on SQL window functions explained covers the mental model that trips up most beginners before you get into practice reps. And if you're using AI to help you study, see our guide on using AI to learn SQL faster for how to do that without accidentally skipping the learning.
Mistakes That Waste Your Prep Time
- Grinding hundreds of unrelated questions instead of focusing on the specific patterns (joins, window functions, aggregations) that show up in almost every interview loop.
- Skipping timed practice entirely and only ever solving problems at your own pace, which doesn't build the speed real interviews require.
- Never reviewing questions you got wrong a second time, a week later, to check whether the concept actually stuck.
- Trusting a company label on a question as a guarantee of what you'll be asked, rather than as a rough style guide.
- Ignoring the "explain your thinking out loud" skill, which many interviewers weigh as heavily as getting the right answer.
Key Takeaways
- No single platform is best for everyone. StrataScratch leads for data-role-specific, company-sourced volume. LeetCode leads for free, reliable fundamentals. DataLemur leads for tight, verified curation.
- Most experienced candidates combine at least two platforms rather than relying on one.
- Free tiers are genuinely usable for full prep if you have enough time; paid tiers mainly buy speed and volume.
- Question count matters less than whether the questions match your actual target role and company style.
- Treat "sourced from a real interview" labels as directional, not a guarantee of your exact interview content.
Frequently Asked Questions (FAQs)
What's the best free SQL interview prep platform?
LeetCode's database section is the largest genuinely free option, with roughly 250 SQL problems that don't sit behind a paywall. DataLemur and StrataScratch both offer smaller free tiers, usually 30 to 50 questions, which is enough to evaluate the platform but not enough for a full prep cycle.
Is StrataScratch or LeetCode better for data analyst interviews?
StrataScratch is generally the better fit for data analyst and data science interviews specifically, since its questions are sourced from real company interviews in data roles and its free plan lets you filter by company. LeetCode's database section is excellent for drilling core SQL syntax but was originally built for software engineering interviews, so a lot of its broader question bank is not relevant to data roles.
How long should I spend prepping for a SQL interview?
For someone with basic SQL knowledge already, two to four weeks of consistent daily practice is a reasonable range for a mid-level role. For a complete beginner, or for a FAANG-level interview loop, six to eight weeks is more realistic, with the final one to two weeks focused specifically on timed, interview-style practice.
Do I need a paid subscription to pass a SQL interview?
Not necessarily. A determined candidate can build solid fundamentals using free tiers across two or three platforms. A paid subscription mainly buys you volume, company-specific question filtering, and in some cases AI-assisted feedback, which speeds up prep but isn't strictly required to pass.
Should I trust platforms that label questions as coming from a specific company, like "Meta SQL interview"?
Treat company labels as directional rather than guaranteed. Interview questions change over time and vary by team even within the same company, so a question labeled as a past Meta interview question is useful for practicing the right style and difficulty, not a guarantee of what you'll actually be asked.
Related Articles
External References
- KDnuggets. "7 Best Platforms to Practice SQL." kdnuggets.com
- Medium. "I Tried the 6 Interview Prep Platforms. Honest Take!" medium.com
- DataLemur. "DataLemur vs. LeetCode for SQL Interviews." datalemur.com
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