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Cumulative Distinct Customers Over Time
Calculate the cumulative number of unique customers over time. For each distinct order_date, show order_date, new_customers (customers ordering for the first time on that date), and cumulative_customers (running total of unique customers up to that date). Sort by order_date. Cumulative distinct counting is a core product analytics question at Meta and Spotify because COUNT(DISTINCT) doesn't work as a window function.
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Schema
orders
| order_id | customer_id | product | category | quantity | price | total | order_date | country | status |
|---|---|---|---|---|---|---|---|---|---|
| 1 | 1 | Laptop Pro | Electronics | 1 | 1299.99 | 1299.99 | 2024-01-15 | USA | completed |
| 2 | 2 | Wireless Mouse | Electronics | 2 | 49.99 | 99.98 | 2024-01-16 | Canada | completed |
| 3 | 3 | Office Chair | Furniture | 1 | 349.99 | 349.99 | 2024-01-17 | USA | completed |
Expected output: Jan-1: new=2, cumulative=2. Jan-2: new=1, cumulative=3
Hint
Concepts
SELECT CTE Window Functions GROUP BY Window Functions + CTE
Practise the topic: SQL practice questions · CTE practice · Window function practice · GROUP BY exercises · Advanced SQL interview questions
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Airbnb · Anthropic · Meta · Netflix · OpenAI · Ramp · Revolut · Snowflake · Spotify · Stripe
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