SQL

Write queries: filtering, joins, grouping, subqueries and window functions.

52 problems

Title	Tags	Acceptance	Difficulty
1. High EarnersSQL	SELECT · WHERE · ORDER BY	—	Easy
2. Employees per DepartmentSQL	GROUP BY · COUNT	—	Easy
3. Second Highest SalarySQL	Subquery · MAX	—	Medium
4. Employee with DepartmentSQL	JOIN	—	Easy
5. Customers Who Never OrderedSQL	LEFT JOIN · NULL	—	Easy
6. Total Spent per CustomerSQL	JOIN · GROUP BY · SUM	—	Medium
7. Duplicate EmailsSQL	GROUP BY · HAVING	—	Easy
8. Above Department AverageSQL	Correlated Subquery	—	Medium
9. Top Earner per DepartmentSQL	Window Functions · RANK	—	Hard
10. Running Total of OrdersSQL	Window Functions · SUM OVER	—	Hard
11. Managers with Two or More ReportsSQL	Self Join · GROUP BY	—	Medium
12. Departments with No EmployeesSQL	NOT EXISTS · LEFT JOIN	—	Easy
13. All StudentsSQL	SELECT	—	Easy
14. Students from ChennaiSQL	WHERE	—	Easy
15. Missing CitySQL	NULL	—	Easy
16. Students per ClassSQL	GROUP BY	—	Easy
17. Average Score per SubjectSQL	JOIN · AVG	—	Easy
18. Total Marks per StudentSQL	JOIN · SUM	—	Medium
19. Topper in Each SubjectSQL	Window Functions	—	Hard
20. Students Without MarksSQL	LEFT JOIN	—	Easy
21. Assign GradesSQL	CASE	—	Medium
22. Passed Every Subject TakenSQL	HAVING · MIN	—	Medium
23. Rank Students in ClassSQL	Window Functions · DENSE_RANK	—	Hard
24. Youngest StudentSQL	ORDER BY · LIMIT	—	Easy
25. Born in 2010SQL	Dates · LIKE	—	Easy
26. Names Starting with a VowelSQL	LIKE · SUBSTR	—	Easy
27. Above the School AverageSQL	Subquery	—	Medium
28. Books by an AuthorSQL	WHERE	—	Easy
29. Books per GenreSQL	GROUP BY	—	Easy
30. Currently Borrowed BooksSQL	JOIN · NULL	—	Easy
31. Most Borrowed BookSQL	GROUP BY · ORDER BY	—	Medium
32. Books Never BorrowedSQL	NOT EXISTS	—	Easy
33. Loan DurationsSQL	Dates · julianday	—	Medium
34. Loans per MemberSQL	LEFT JOIN · COUNT	—	Medium
35. Authors with Several BooksSQL	HAVING	—	Easy
36. Classic BooksSQL	WHERE · BETWEEN	—	Easy
37. Available CopiesSQL	Subquery · COALESCE	—	Hard
38. Members Who Joined in 2024SQL	Dates	—	Easy
39. First Loan of Each MemberSQL	Window Functions · ROW_NUMBER	—	Hard
40. Salary BandsSQL	CASE · GROUP BY	—	Medium
41. Department PayrollSQL	JOIN · SUM	—	Easy
42. Recent HiresSQL	Dates	—	Easy
43. Employee and ManagerSQL	Self Join · LEFT JOIN	—	Medium
44. Third Highest SalarySQL	DISTINCT · LIMIT OFFSET	—	Medium
45. Share of Department PayrollSQL	Window Functions	—	Hard
46. Email DomainsSQL	String Functions	—	Medium
47. Monthly RevenueSQL	Dates · GROUP BY	—	Medium
48. Orders by CitySQL	JOIN · GROUP BY	—	Easy
49. Customer with the Largest OrderSQL	Subquery	—	Easy
50. Repeat CustomersSQL	HAVING	—	Easy
51. Order vs Previous OrderSQL	Window Functions · LAG	—	Hard
52. Revenue Share by CustomerSQL	Subquery	—	Medium

52 of 52 problems