Five platforms cover most SQL learning and interview-prep traffic in 2026: SQL Quest, DataLemur, StrataScratch, LeetCode SQL, HackerRank SQL. Each one optimizes for a different job-to-be-done. This is the side-by-side that helps you pick — including where each competitor genuinely wins.
Disclosure: SQL Quest is one of the platforms compared. We've tried to flag every place a competitor wins.
Each card has a tagline, a summary, the candidate it's best for, and a link to the full side-by-side.
200+ free challenges, AI Coach (Claude-powered) that explains why your query is wrong, 10-axis adaptive skill radar, session memory, wrong-answer diagnostic that tells you which row mismatched and why. Built for actual SQL learning — not just question grinding or certificate completion.
Real SQL interview questions sourced from Meta, Google, Amazon, and other tier-1 companies, with verified provenance. Solution videos by Nick Singh (Ace the Data Science Interview). Free tier ~30-50 questions, Premium ~$15/month or $300 lifetime. No AI tutor; standard "wrong, try again" feedback loop.
500-700+ questions across SQL and Python, sourced from real interviews. Aggressive paywall — free tier ~50 questions, Premium ~$39/month or $159/year. Strong for data scientist roles that test both languages. No AI tutor or wrong-answer diagnostic.
~250+ SQL problems within LeetCode's broader algorithm/DS/system-design platform. Free tier ~50-80 SQL questions, Premium ~$35/month covers the entire platform. Industry-standard brand, huge active community. SQL is one track among many — no SQL-specialized tutor experience.
~50 SQL questions plus the SQL Skills Certification (Basic / Intermediate / Advanced) — free for individuals. Industry-standard for employer assessments — many companies use HackerRank to screen candidates. Cert recognized on resumes, but doesn't substitute for actual interview readiness.
Verified July 2026. Mobile users — swipe horizontally on the matrix.
Pricing and features change — check each platform's site for the latest. Last verified July 2026.
Answer one question. Pick the platform.
"I'm learning SQL from zero — never written a SELECT statement."
Pick: SQL Quest. The 6-step path with placement check, AI Coach explaining concepts in plain English, foundational skill floor that prevents getting pushed into Hard challenges before you're ready. Other platforms assume SQL knowledge.
"I know SQL basics. I'm prepping for a Meta/Google/Amazon interview in 1-2 weeks."
Pick: DataLemur or StrataScratch for the verified-provenance question bank. Use SQL Quest's free tier as a tutor when you get stuck — paste any DataLemur question into the AI Coach for diagnosis.
"I'm prepping for a software engineer role with algorithms + SQL."
Pick: LeetCode for the algorithm bank (industry standard). Use SQL Quest's free tier for the SQL round — the diagnostic loop teaches faster than LeetCode's "Wrong Answer + expected output."
"I'm a data scientist candidate — interviews test both SQL and Python."
Pick: StrataScratch for the combined SQL + Python question bank. SQL Quest's free tier for SQL specifically when you want diagnostic feedback.
"I want a credential to put on my LinkedIn / resume."
Pick: HackerRank for the SQL Skills Certification. A few hours of work for the credential. Then build real proficiency on SQL Quest.
"I want one platform that handles my whole prep, free tier, no paywall."
Pick: SQL Quest. 200+ challenges across all difficulties, AI Coach, skill radar, sector tracks, all 12 company landings — all free. No other platform's free tier covers this much ground.
"I'm stuck. I keep getting 'incorrect' and don't know what's wrong with my queries."
Pick: SQL Quest. The wrong-answer diagnostic was built for exactly this scenario. Specific row + column + value + reason, not just "incorrect, try again."
"I want to use a platform that the company I'm applying to also uses."
Pick: HackerRank if they use HackerRank for assessments. Familiarity with the same UI on assessment day matters. After that, switch to SQL Quest for the actual learning.
Most candidates can ship interviews on free tiers if they pick the right platform.
SQL Quest
200+ FREE
$29/mo · $99/yr
$199 lifetime
DataLemur
~30-50 FREE
~$29/mo
~$300 lifetime
StrataScratch
~50 FREE
~$39/mo · ~$159/yr
No lifetime
LeetCode SQL
~50-80 FREE
~$35/mo · ~$159/yr
No lifetime
HackerRank SQL
FREE
Free for individuals
Cert: free
Not interview-prep platforms exactly, but they come up in "best free SQL practice" searches. Here's where each fits — and where it stops.
A free, well-loved set of interactive SQL lessons that teach syntax from scratch in the browser — no signup. Excellent for your very first hour with SELECT and JOIN. Stops at the basics: no interview questions, no diagnostic feedback, no Hard problems, and it hasn't changed much in years.
A long-running free tutorial site with progressive exercises (Nobel winners, world countries datasets). Genuinely free and browser-based. The UI is dated, feedback is pass/fail only, and the question style is academic rather than interview-shaped. Good for drilling clause syntax; weak for interview patterns like window functions under pressure.
Mode's free SQL tutorial teaches querying in an analytics context with real-ish datasets, aimed at aspiring analysts. Strong written explanations. It's a tutorial, not a practice bank — a fixed reading path, not a graded challenge loop, and no AI help when you're stuck on your own query.
A structured beginner SQL course with a polished editor. The intro course is free; the full path and projects sit behind Codecademy Pro (~$25-40/mo). Course-shaped and hand-holding — great for total beginners who want a guided curriculum, less useful for interview-specific pattern drilling or diagnostic feedback on your own wrong queries.
Pattern: the free tutorials (SQLBolt, SQLZoo, Mode, Codecademy) teach you to write SQL. The practice platforms (SQL Quest, DataLemur, StrataScratch, LeetCode) train you to pass an interview. Most people do a tutorial first, then a practice platform. SQL Quest is the rare one that does both — a beginner path and a graded interview loop.
We created a free account (or used the no-signup flow) on each platform and worked through its actual onboarding as a candidate would. For every platform we counted the number of questions genuinely accessible on the free tier, checked the listed pricing on the provider's own pricing page, and solved several problems to feel the wrong-answer feedback loop first-hand. Feature claims in the matrix reflect what was live and reachable, not marketing copy. Question counts are approximate because providers change their banks frequently — we round to ranges and re-verify on each update. Where a competitor genuinely does something better than SQL Quest (larger banks, verified provenance, solution videos, Python coverage, employer-recognized certificates), we say so plainly; a comparison that never admits the other side wins isn't a comparison, it's an ad. This page was last re-verified in July 2026. If you spot something out of date, the pricing or feature likely changed on the provider's side since — always confirm on their site before paying.
SQL Quest's free tier is generous because we want you to try the wrong-answer diagnostic before you commit to anything. Open the app, write a deliberately wrong query, see what happens.
Try SQL Quest Free ⚡Read the deep-dive: 📋 Ranked review · vs DataLemur · vs StrataScratch · vs LeetCode SQL · vs HackerRank SQL