Longest Gap Between Orders

For each customer return the longest gap in days between two consecutive orders (NULL if the customer has fewer than two orders). Order by customer_id.

Table schema

Orders(id INT PRIMARY KEY, customer_id INT, order_date DATE)

Sample data

id | customer_id | order_date
1 | 1 | 2026-01-01
2 | 1 | 2026-01-11
3 | 1 | 2026-02-20
4 | 2 | 2026-03-01