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Membership × Country Activity (Cross Join)
Marketing wants a membership-tier × country activity grid: every (membership, country) cell with the count of orders placed by customers of that tier from that country — including empty cells.
CROSS JOIN distinct memberships (from customers) with distinct countries (from orders), then LEFT JOIN orders + customers to count. Show membership, country, order_count (0 when none). Order by membership, then country.
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Schema
customers
| customer_id | name | signup_date | membership | total_orders | |
|---|---|---|---|---|---|
| 1 | John Smith | john.smith@email.com | 2023-01-15 | Gold | 15 |
| 2 | Emma Wilson | emma.wilson@email.com | 2023-03-20 | Silver | 8 |
| 3 | Michael Brown | michael.brown@email.com | 2023-02-10 | Gold | 12 |
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: 28 rows, many with order_count = 0
Hint
SELECT, CROSS JOIN, LEFT JOIN, and open the hint there if you stall.Concepts
SELECT CROSS JOIN LEFT JOIN GROUP BY Cross Join
Practise the topic: SQL practice questions · JOIN practice · GROUP BY exercises
Read the concept: LEFT JOIN vs INNER JOIN
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