Database Practice Sheet

A curated path of 20+ real SQL problems from LeetCode to help you practice database fundamentals. Organized by difficulty, each item includes a direct link to a working problem.

Filters

• Beginner
• Intermediate
• Advanced

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Beginner

1. Second Highest Salary – Subquery / Ranking – LeetCode Problem
2. Delete Duplicate Emails – DELETE with conditions – LeetCode Problem
3. Customers Who Never Order – LEFT JOIN + NULL – LeetCode Problem
4. Combine Two Tables – Simple JOIN – LeetCode Problem
5. Rearrange Products Table – SELECT with CASE – LeetCode Problem
6. Group Sold Products By Date – GROUP BY – LeetCode Problem
7. Queries Quality and Percentage – Aggregation / ROUND – LeetCode Problem
8. Trips and Users – JOIN + GROUP BY – LeetCode Problem

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Intermediate

9. Employees That Report to Each Employee – Self-Join + Aggregation – LeetCode
10. Rank Scores – Dense Rank Simulation – LeetCode
11. Department Top Three Salaries – Window Function Simulation – LeetCode
12. Highest Altitude – Window Function / Cumulative Sum – LeetCode
13. Employees Earning More Than Their Managers – Subquery + Comparison – LeetCode
14. Customers Who Made Multiple Orders – GROUP BY + HAVING – LeetCode
15. Delete Duplicate Emails – DELETE with Conditions – LeetCode
16. Customers Who Never Order – LEFT JOIN + NULL Test – LeetCode

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Advanced

17. SQL 50 Study Plan – Comprehensive SQL Topics – LeetCode
18. Full Database Problem Set – Explore All Problems – LeetCode
19. Average Salary: Departments VS Company – GROUP BY + CTE (Prime access) – LeetCode
20. List the Products Ordered in a Period – Filtering + Aggregation - LeetCode

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:::tip Tip Use LeetCode’s in-browser SQL editor to run queries. Always review test cases and community discussions for insight and edge-case handling. :::

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