SELECT
 full_name,
 jumlah_peminjaman,
 (CASE WHEN (jumlah_peminjaman < 40) THEN '10%'
 WHEN (jumlah_peminjaman >= 40) AND (jumlah_peminjaman < 60) THEN '20%'
 WHEN (jumlah_peminjaman >= 60) THEN '30%'
 END) AS diskon
FROM (
 SELECT
  CONCAT(first_name,' ',last_name) AS "full_name",
  COUNT(rental.rental_id)+COUNT(payment.payment_id) AS jumlah_peminjaman
 FROM
  customer INNER JOIN rental ON (customer.customer_id = rental.customer_id) INNER JOIN payment ON (rental.rental_id=payment.rental_id)
 GROUP BY first_name, last_name
) AS T1