怎me写sql，可以将weight列按年份求和？

要将weight列按年份求和，但是date列要显示到月份，这个sql应该怎么写。

mysql :select v.total ,right(v.date_code,2) month from (select sum(weight) total , date_code from t group by date_code ) v

db2有over partition by这种开窗函数吗，有的话可以用下面的语句试试。

select sum(weight) over(partition by left(date_code,4)) total , right(v.date_code,2) month from t1;