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Top SQL Interview Questions with Answers for Data Analysts (2026 Guide)

If you want to crack SQL interviews, you must think like a Data Analyst, not just someone who writes queries.

This guide covers real-world SQL interview questions including window functions, joins, duplicates, and business scenarios.

👉 If you're also learning Python for data roles, check this guide: Python Automation Opportunities (Complete Guide)

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🧠 SQL Interview Question (First Time a Product Became Top Seller)

Table:

sales(product_id, sale_date, revenue)

Question:

👉 Find the first date each product became the highest revenue generator of that day

💡 SQL Solution

WITH ranked AS (
    SELECT 
        product_id,
        sale_date,
        revenue,
        RANK() OVER (
            PARTITION BY sale_date 
            ORDER BY revenue DESC
        ) AS rnk
    FROM sales
),
top_days AS (
    SELECT 
        product_id,
        sale_date
    FROM ranked
    WHERE rnk = 1
)
SELECT 
    product_id,
    MIN(sale_date) AS first_top_date
FROM top_days
GROUP BY product_id;

🔥Why This Question Is Powerful ..

Tests window functions deeply 🧠

* Mix of ranking + aggregation

* Real-world business scenario (top performer tracking)

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🔥 SQL Scenario-Based Interview Questions (Most Asked)

📊 Q1. How do you optimize slow SQL queries?

• 👉 Check execution plan
• 👉 Add proper indexes
• 👉 Avoid SELECT *
• 👉 Optimize joins & filters

👉 Learn more about data optimization concepts: Data Analysis Tutorials

📊 Q2. How to find duplicate records?

• 👉 Use GROUP BY with HAVING COUNT(*) > 1
• 👉 Or use ROW_NUMBER() with PARTITION BY
• 👉 Identify duplicates based on key columns

📊 Q3. How to get 2nd highest salary?

• Use subquery with MAX()
• 👉 Or use DENSE_RANK() / ROW_NUMBER()
• 👉 Handle duplicates carefully

📊 Q4. INNER JOIN vs LEFT JOIN?

• 👉 INNER JOIN → only matching records
• 👉 LEFT JOIN → all left + matched right
• 👉 Use LEFT JOIN when missing data matters

📊 Q5. Handling NULL values?

• Use COALESCE() / ISNULL()
• 👉 Be careful in comparisons (NULL ≠ 0)
• 👉 Handle NULLs in aggregations properly

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🧠 SQL Interview Question (Products Bought Together)

Table:

order_items(order_id, product_id)

Question:

👉  Find pairs of products that are frequently bought together in the same order

Return product_id_1, product_id_2, pair_count

🧩 How Interviewers Expect You to Think

* Self-join on same order 🛒

* Avoid duplicate/reverse pairs

* Count frequency of each pair

💡 SQL Solution

SELECT 
    o1.product_id AS product_id_1,
    o2.product_id AS product_id_2,
    COUNT(*) AS pair_count
FROM order_items o1
JOIN order_items o2 
    ON o1.order_id = o2.order_id
    AND o1.product_id < o2.product_id
GROUP BY 
    o1.product_id,
    o2.product_id
ORDER BY pair_count DESC;

🔥 Why This Matters: * Classic market basket analysis 🧠

* Tests self-join + combinations logic

* Frequently asked in e-commerce & analytics roles

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📚 Must Learn Topics for SQL Interviews

• Window Functions (RANK, DENSE_RANK)
• Joins (INNER, LEFT)
• Aggregations
• CTE (WITH)
• Subqueries

👉 Start learning coding basics here: Python Programming Tutorials

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❓ FAQ (SEO Boost)

What SQL questions are asked in interviews?

Joins, window functions, duplicates, NULL handling, ranking, and real-world scenarios.

Is SQL enough for data analyst jobs?

SQL + Excel + Python is the best combination.

How to practice SQL effectively?

Practice real scenario-based questions and explain business logic.

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 Conclusion

SQL interviews are about thinking, not just coding.

👉 Focus on logic 👉 Understand business problems 👉 Practice real questions

💡 Want to boost your earning skills? Read this: Python Automation Guide

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