🧠 SQL Interview Question (Running Total of Sales)
📌

sales(order_id, order_date, amount)

❓ Ques :

👉 Calculate the running total of sales for each day

👉 Return order_date, daily_sales, running_total

🧩 How Interviewers Expect You to Think

• Aggregate sales per day 📊
• Use window function for cumulative sum
• Order data correctly for running calculation

💡 SQL Solution

WITH daily_sales AS (
SELECT
order_date,
SUM(amount) AS daily_sales
FROM sales
GROUP BY order_date
)

SELECT
order_date,
daily_sales,
SUM(daily_sales) OVER (
ORDER BY order_date
) AS running_total
FROM daily_sales;

🔥 Why This Question Is Powerful

• Tests window functions (must-know) 🧠
• Very common in real-world reporting
• Frequently asked in analyst & BI roles

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