How to sum with a condition?

Question

Google Sheets

Good afternoon.
The question is:
There are two sheets (Sheet1, Sheet2). The first one has column A with dates. Column B with numbers
The second sheet has a column A with dates, and column B of Sheet2 should be with the sum of all the numbers of column B of Sheet1, the date A of Sheet1 that is not greater than the date A of Sheet2
Example:
Sheet1:

Sheet2:

I have no idea at all. I'm trying to play with SUMIF, but nothing comes out at all. Please, help.

Answer 1

There are a couple of killer features in Google Sheets, namely FILTER () and QUERY ()
The first one will suit you (enter into Sheet2 B1, spread down )
=СУММ( FILTER(Лист1!B:B;Лист1!A:A<=A1) )
: which Sheet1!A:A<=A1 . What happens is cumulative.