🧠 SQL Interview Question (Moderate & Revenue Analysis)
📌

orders(order_id, customer_id, order_amount)

❓ Ques :

👉 Find customers who contribute more than 30% of the total company revenue.

🧩 How Interviewers Expect You to Think

• Calculate overall total revenue
• Aggregate revenue at customer level
• Compare individual contribution against total
• Avoid recalculating total multiple times inefficiently

💡 SQL Solution

WITH total_revenue AS (
SELECT SUM(order_amount) AS total_rev
FROM orders
),
customer_revenue AS (
SELECT
customer_id,
SUM(order_amount) AS cust_rev
FROM orders
GROUP BY customer_id
)
SELECT c.customer_id
FROM customer_revenue c
CROSS JOIN total_revenue t
WHERE c.cust_rev > 0.30 * t.total_rev;

🔥 Why This Question Is Powerful

• Tests percentage-based business logic
• Evaluates ability to combine multiple aggregations
• Reflects real-world Pareto (80/20) analysis scenarios
• Common in product, growth & revenue analytics interviews

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