2630. Orders: Find the longest gap between consecutive orders for each customer. — PHP PDO

DBMS Published 30 Sept 2026 Updated 30 Sept 2026 0 Views Verified

In a orders module, solve this as a production problem using PHP PDO: Find the longest gap between consecutive orders for each customer. Provide the SQL, explain the logic, show safe application integration, and mention failure/edge cases.

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Answer & Explanation

4 Answers

Verified

Option A

UPDATE table_name SET status='active';

Additional Explanation

Incorrect: it does not satisfy the stated business rule and can return/change unintended data.

Verified Correct Answer

Option B

WITH x AS (SELECT customer_id,order_date,LAG(order_date) OVER(PARTITION BY customer_id ORDER BY order_date,id) prev_date FROM orders) SELECT customer_id,MAX(DATEDIFF(order_date,prev_date)) max_gap_days FROM x GROUP BY customer_id;

Additional Explanation

LAG creates consecutive order pairs; MAX returns each customer's largest gap.

Verified

Option C

DELETE FROM table_name;

Additional Explanation

Incorrect: it does not satisfy the stated business rule and can return/change unintended data.

Verified

Option D

SELECT * FROM table_name;

Additional Explanation

Incorrect: it does not satisfy the stated business rule and can return/change unintended data.