50 Must-Know SQL Concepts

📍 Core Concepts  

1. SELECT, FROM, WHERE  

2. ORDER BY, LIMIT  

3. AND, OR, NOT, IN, BETWEEN  

4. NULL & IS NULL  

5. DISTINCT  

📍 Aggregations  

6. COUNT(), SUM(), AVG()  

7. MIN(), MAX()  

8. GROUP BY  

9. HAVING  

📍 Joins  

10. INNER JOIN  

11. LEFT JOIN  

12. RIGHT JOIN  

13. FULL OUTER JOIN  

14. SELF JOIN  

15. CROSS JOIN  

📍 Subqueries & CTEs  

16. Subquery in SELECT  

17. Subquery in WHERE  

18. WITH (Common Table Expression)  

19. Correlated Subqueries  

📍 Window Functions  

20. ROW_NUMBER()  

21. RANK(), DENSE_RANK()  

22. LEAD(), LAG()  

23. OVER(), PARTITION BY  

📍 String & Date Functions  

24. CONCAT(), LENGTH(), UPPER()/LOWER()  

25. SUBSTRING(), REPLACE()  

26. DATE(), NOW(), DATEDIFF()  

📍 Advanced Features  

27. CASE WHEN  

28. IF() & IFNULL()  

29. COALESCE()  

30. Nested Queries  

31. Temporary Tables  

32. Views  

33. Stored Procedures (Basic)  

34. Indexes & Performance  

35. Transactions (BEGIN, COMMIT, ROLLBACK)  

36. Primary & Foreign Keys  

📍 Analytics Use Cases  

37. Cohort Analysis  

38. Retention Metrics  

39. Funnel Analysis  

40. Rolling Averages  

41. AB Testing Query Logic  

📍 Best Practices

42. Aliasing (AS)  

43. Use EXPLAIN to check query plan  

44. Avoid SELECT * in production  

45. Proper indexing  

46. Normalize vs Denormalize  

📍 Real-Life Scenarios  

47. Querying large datasets  

48. Optimizing slow queries  

49. Joining multiple large tables  

50. Writing reusable queries