SQL & PL/SQL

Hi

Could someone tell me how I update field: 0 or 1 in table1 below. In this example Customer 1 should get values 1 in rows one and two, because his sum of amount is bigger than 15 in month 2. Other rows are null in this example.

table1

year     month     customer    amount     0 or 1

2018         2               1             10                           row1

2018         2               1             10                           row2

2018         2               2              3                            row3

2018         2               2              2                            row4

2018         1               2              10                          row5

select year,month,customer,sum(amount)

from table

group by year,month,customer

having sum(amount) > 15