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500+ real-world SQL questions • Interactive Excel grids • AI-powered debugging • Track progress • Export resume badges & certificates.

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500+
Questions
Real
Company Tags
AI
Helper

Everything You Need to Ace Interviews

Real interview questions, interactive Excel practice, AI help, resume export & more — all in one place.

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500+ Real SQL Problems

Easy → Hard • Company-tagged (FAANG, Startups) • Window functions, JOINs, CTEs, optimization
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Interactive Excel Practice

Handsontable grids • Formulas • Pivot simulation • VLOOKUP / INDEX-MATCH tasks
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AI-Powered Tutor

Ask "why this JOIN fails?" • Get hints, explanations, optimized versions instantly
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Resume & Shareable Achievements

Badges • PDF certificates • Completed questions list • LinkedIn-ready share text
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Progress & Streaks

Daily streaks • Leaderboard • Difficulty filters • Company mock interviews
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Offline-first & Fast

SQLite in browser • No login required to start • Save progress locally
✦ Step-by-step walkthrough

How to Use DataHouz

Go from zero to solving real interview questions in under 5 minutes. Here is exactly what the experience looks like.

1

Pick any question

Browse 500+ questions filtered by difficulty, topic, or company. Each question shows you the difficulty badge, topic tag, and which company asks it in real interviews.

  • ✓ Filter by Easy / Medium / Hard
  • ✓ Filter by company — Google, Amazon, Microsoft and more
  • ✓ Filter by topic — JOIN, Window, CTE, Subquery
  • ✓ Green tick shows questions you have already solved
Question List
All Difficulty
All Topics
All Companies
✓
Top 3 salaries per department
HARD Window Google
Solved ✓
○
Second Highest Salary
MEDIUM Subquery Microsoft
Unsolved
○
Retrieve Full Customer Profile
EASY JOIN Amazon
Unsolved
Problem Statement
Problem #7 · Window
7 / 84
Top 3 salaries per department
HARD Window Google
You have a table called employees. Find the top 3 highest-paid employees in each department. Include ties — if two employees share the same salary both should appear.
employees · 7 cols · 6 rows
Column
Type
Key
id
INT
PK
name
VARCHAR
salary
INT
dept_id
INT
FK
2

Read the question and schema

Every question shows a clear problem statement, the database schema with column names and types, and sample input/output so you know exactly what your query should return.

  • ✓ Clear table structure with PK / FK labels
  • ✓ Real sample data pre-loaded in the browser database
  • ✓ Expected output shown so you know what to aim for
  • ✓ Navigate Prev / Next without losing your place
3

Write your SQL and get hints

Type your SQL in the editor and click Run to see instant results. Stuck? Unlock step-by-step hints one at a time — each hint nudges you closer without giving the full answer away.

  • ✓ Live SQL editor with syntax highlighting
  • ✓ Ctrl+Enter shortcut to run quickly
  • ✓ 3 progressive hints — unlock one at a time
  • ✓ Smart error messages that tell you exactly what went wrong
SQL Editor Ctrl+Enter = Run
SELECT dept_id, name, salary, rnk
FROM (
  SELECT dept_id, name, salary,
    DENSE_RANK() OVER (
      PARTITION BY dept_id
      ORDER BY salary DESC
    ) AS rnk
  FROM employees
) ranked
WHERE rnk <= 3;
Step-by-step hints — 2 of 3 revealed
✓ Hint 1 — Use DENSE_RANK() so tied salaries share the same rank
✓ Hint 2 — Add PARTITION BY dept_id to reset rank per department
🔒Hint 3 — unlock if you need more help
Result Panel
dept_id
name
salary
rnk
1
Vikram Singh
110000
1
1
Priya Patel
92000
2
1
Rahul Sharma
75000
3
2
Sneha Gupta
68000
1
2
Neha Joshi
55000
2
✓ 5 rows returned · matches expected output
🏆
Correct Answer! 🎉
Solved and saved to your profile
24 Mar · 5 rows · ✓
4

Submit and see instant feedback

Click Submit and DataHouz instantly checks your answer against the expected output. See your result table, whether rows match, and your accuracy score — all in real time.

  • ✓ Instant correct / wrong feedback with row comparison
  • ✓ Solution saved to your profile automatically
  • ✓ Share your solution on LinkedIn in one click
  • ✓ Wrong answer? See exactly where your output differs
5

Track progress and earn badges

Your dashboard tracks everything — questions solved, daily streak, accuracy rate, and performance level. Earn badges and export a PDF certificate to add to your resume or LinkedIn profile.

  • ✓ Dashboard with solved count, streak, and level
  • ✓ Badges for milestones — First Solve, 10 Streak, Hard Solver
  • ✓ Export PDF certificate with your solved questions
  • ✓ Progress synced to cloud — access from any device
Dashboard
24
SQL Solved
7🔥
Day Streak
Inter-
mediate
Level
Badges Earned
🥇
First Solve
🔥
7 Streak
💎
Hard Solver
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Locked
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