Hive. Over partition by vs where conditions
In order to make use of the partitions -

Your query on the whole month should look something like this:

select      col1,col2,sum(col3),year,month,day
from        mytale
where       year  = '2017'
        and month = '02'
group by    col1,col2,year,month,day


Your query on a single day should look something like this:

select      col1,col2,sum(col3),year,month,day
from        mytale
where       year  = '2017'
        and month = '02'
        and day   = '01'
group by    col1,col2,year,month,day


Your query on a range of days should look something like this:

select      col1,col2,sum(col3),year,month,day
from        mytale
where       year  = '2017'
        and month = '02'
        and day between '01' and '07'
group by    col1,col2,year,month,day