Windowing function output path syntax

Hello,

I am trying to use the windowing function and wondering how can I save the output into an existing table in hive.

for. eg. Trying to run this 
from t_enc
partition by mid
order by tdate
with
sum(tamt) as slsamt 
select mid,tdate,slsamt;

I would like to save the output to an existing table and not sure how can I do that.

Please advise.

Thanks!
