Longest Call per Customer

Return each customer's longest call length in minutes. Order by customer.

Table schema

Calls(id INT PRIMARY KEY, customer VARCHAR(10), minutes INT, call_date DATE)

Sample data

id | customer | minutes | call_date
1 | Ann | 30 | 2026-04-01
2 | Ann | 50 | 2026-04-02
3 | Bob | 20 | 2026-04-01
4 | Cy | 70 | 2026-04-03
5 | Cy | 45 | 2026-04-04
6 | Bob | 15 | 2026-04-05