How many transactions payment made by customer that is lower than 10000. Group the result by year.
Transactions payment lower than 10000 refer to COUNT(amount) < 1000; by year refers to YEAR(paymentDate)
SELECT STRFTIME('%Y', t1.paymentDate), COUNT(t1.customerNumber) FROM payments AS t1 WHERE t1.amount < 10000 GROUP BY STRFTIME('%Y', t1.paymentDate)