✅ 50 Must-Know SQL Concepts for Interviews 🧠📊

📍 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

💡 Tap ❤️ for more!