1. What are the different types of joins in SQL, and how do they differ?
2. Explain how a self-join works in SQL.
3. What is the difference between a left join and an inner join?
4. How do you implement conditional joins in SQL?
5. What is a cross join, and when would you use it?
6. How do you use the UNION ALL operator, and how is it different from UNION?
7. Explain the concept of set operations in SQL.
8. What is the purpose of the EXCEPT operator in SQL?
9. How do you implement subqueries in SQL, and what are their types?
10. When would you prefer to use a subquery instead of a join?
11. What is a correlated subquery?
12. How do you optimize subqueries for better performance?
13. What are indexes, and why are they important?
14. How do you create a composite index in SQL?
15. What are the benefits and drawbacks of using indexes?
16. How do you analyze and optimize query performance in SQL?
17. What is query execution plan, and how can it help optimize queries?
18. What is the purpose of the EXPLAIN PLAN statement?
19. How do you use database statistics to improve query performance?
20. What are the differences between clustered and non-clustered indexes?
21. How do you handle duplicate values in a query result?
22. What is the purpose of the ROW_NUMBER() window function?
23. How do you implement pagination using the OFFSET and FETCH clauses?
24. What are window functions, and how do they differ from aggregate functions?
25. How do you calculate running totals using window functions?
26. What is the purpose of the PARTITION BY clause in SQL?
27. How do you create and use common table expressions (CTEs)?
28. What is the difference between a recursive CTE and a non-recursive CTE?
29. How do you implement a pivot table in SQL?
30. What is the PIVOT operator, and how does it work?
31. How do you unpivot data in SQL?
32. What are materialized views, and how do they differ from regular views?
33. How do you refresh a materialized view, and what options do you have?
34. What is the purpose of the MERGE statement in SQL?
35. How do you implement an upsert operation using the MERGE statement?
36. What are transactions, and how do they ensure data integrity?
37. What is the difference between implicit and explicit transactions?
38. How do you manage transaction isolation levels in SQL?
39. What are the four main transaction isolation levels?
40. How do you handle deadlocks in SQL?