Sum all field with the other field < itself in sqlite

Sorry because I dont think good title for my problem. I have table a(f1 integer, date Long), date increase, and the data

f1       date
1        1
2        2
3        3
...

I need to sum f1 by date, with record 1{1,1} the sum f1 is 1,with record 2 the sum f1 is 1+2, record 3 the sum f1 is 1+2+3... How can I do that?