Customers With Several Open Loans

A loan is open when payments are less than its principal. Return customers with more than one open loan, and how many.

Table schema

Loans(id INT PRIMARY KEY, customer VARCHAR(10), principal INT, annual_rate INT, months INT)
Payments(loan_id INT, amount INT, paid_on DATE)

Sample data

Loans
id | customer | principal | annual_rate | months
1 | Ann | 1000 | 12 | 6
2 | Bob | 2000 | 10 | 12
3 | Ann | 500 | 8 | 3
4 | Bob | 300 | 5 | 3

Payments
loan_id | amount | paid_on
1 | 400 | 2026-02-01
1 | 600 | 2026-03-01
2 | 500 | 2026-02-05
2 | 500 | 2026-03-05