✅ 50 Must-Know SQL Concepts for Interviews
A complete roadmap of SQL topics every data professional should master 🧠📊
This checklist-style SQL guide helps you revise fundamentals → advanced → real-world use cases.
Ideal for interview prep, quick refreshers, and self-assessment.
📍 Core Concepts
- 1️⃣ SELECT, FROM, WHERE
- 2️⃣ ORDER BY, LIMIT
- 3️⃣ AND, OR, NOT, IN, BETWEEN
- 4️⃣ NULL & IS NULL
- 5️⃣ DISTINCT
📍 Aggregations
- 6️⃣ COUNT(), SUM(), AVG()
- 7️⃣ MIN(), MAX()
- 8️⃣ GROUP BY
- 9️⃣ HAVING
📍 Joins
- 🔟 INNER JOIN
- 1️⃣1️⃣ LEFT JOIN
- 1️⃣2️⃣ RIGHT JOIN
- 1️⃣3️⃣ FULL OUTER JOIN
- 1️⃣4️⃣ SELF JOIN
- 1️⃣5️⃣ CROSS JOIN
📍 Subqueries & CTEs
- 1️⃣6️⃣ Subquery in SELECT
- 1️⃣7️⃣ Subquery in WHERE
- 1️⃣8️⃣ WITH (Common Table Expression)
- 1️⃣9️⃣ Correlated Subqueries
📍 Window Functions
- 2️⃣0️⃣ ROW_NUMBER()
- 2️⃣1️⃣ RANK(), DENSE_RANK()
- 2️⃣2️⃣ LEAD(), LAG()
- 2️⃣3️⃣ OVER(), PARTITION BY
📍 String & Date Functions
- 2️⃣4️⃣ CONCAT(), LENGTH(), UPPER(), LOWER()
- 2️⃣5️⃣ SUBSTRING(), REPLACE()
- 2️⃣6️⃣ DATE(), NOW(), DATEDIFF()
📍 Advanced Features
- 2️⃣7️⃣ CASE WHEN
- 2️⃣8️⃣ IF() & IFNULL()
- 2️⃣9️⃣ COALESCE()
- 3️⃣0️⃣ Nested Queries
- 3️⃣1️⃣ Temporary Tables
- 3️⃣2️⃣ Views
- 3️⃣3️⃣ Stored Procedures (Basic)
- 3️⃣4️⃣ Indexes & Performance
- 3️⃣5️⃣ Transactions (BEGIN, COMMIT, ROLLBACK)
- 3️⃣6️⃣ Primary & Foreign Keys
📍 Analytics Use Cases
- 3️⃣7️⃣ Cohort Analysis
- 3️⃣8️⃣ Retention Metrics
- 3️⃣9️⃣ Funnel Analysis
- 4️⃣0️⃣ Rolling Averages
- 4️⃣1️⃣ A/B Testing Query Logic
📍 Best Practices
- 4️⃣2️⃣ Aliasing (AS)
- 4️⃣3️⃣ Use EXPLAIN to analyze query plans
- 4️⃣4️⃣ Avoid SELECT * in production
- 4️⃣5️⃣ Proper indexing strategy
- 4️⃣6️⃣ Normalize vs Denormalize
📍 Real-Life Scenarios
- 4️⃣7️⃣ Querying large datasets
- 4️⃣8️⃣ Optimizing slow queries
- 4️⃣9️⃣ Joining multiple large tables
- 5️⃣0️⃣ Writing reusable and scalable queries
🚀 Interview Tip: If you can confidently explain and use these 50 concepts,
you are interview-ready for most SQL roles.
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