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Customer × day activity grid

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Customer × day activity grid

Build a complete grid of customer × day combinations: for customers c_001, c_002, c_003 across days 2026-05-10, 2026-05-11, 2026-05-12 (3 customers × 3 days = 9 rows). For each combination return the count of orders that customer placed that day (0 if none — including c_003 who has no orders ever).

Use CROSS JOIN of the customer set and the date spine, then LEFT JOIN orders.

Columns: customer_id, day, order_count. Sort by customer_id then day ascending.

Tables & sample data

customers

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orders

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query.sql

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