select * from payment;
select customer_id,
sum(amount) 'Total amount',
ROUND((datediff(current_date,payment_date))/30,0) 'Month_till_Now'
from payment
WHERE
rental_id<9999
AND rental_id IS not null
AND customer_id not in (30,90)
AND customer_id not LIKE '5%'
GROUP BY customer_id
,Month_till_Now
ORDER by
sum(amount) desc,
customer_id asc
;
这个语句执行了之后ustomer_id没有升序