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Customers who never ordered

SQL data engineering interview problem. Difficulty: beginner. Pattern: Joins. About 8 minutes. Part of the Pro drill bank.

Using customers and lb_orders, find customers who have never placed an order. Columns: customer_id, name. Order by customer_id. Prefer LEFT JOIN ... WHERE order_id IS NULL (problem 48 revisits NOT EXISTS).

Constraints

  • lb_orders is the order table for this study set (not orders).

Examples

Input: customers lb_orders customer_id | name customer_id C03 | Cam C03 C04 | Dee (no rows) C05 | Eli (no rows) Output: customer_id | name C04 | Dee C05 | Eli Why this passes: Cam has orders. Dee and Eli have none.

Topics: lakebench, sql, anti-join, left join.

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beginner

Customers who never ordered

Interview-style drill: Anti-join customers with no rows in lb_orders.

Using `customers` and `lb_orders`, find customers who have never placed an order. Columns: `customer_id`, `name`. Order by `customer_id`. Prefer LEFT JOIN ... WHERE order_id IS NULL (problem 48 revisits NOT EXISTS).