Use most recent date for missing dates when joining tables

Question

I have 2 tables:

1.tran_test : (id, amount, currency(Currency_Name), date_1)
2.cur_test: (id, currency, date_2, price(amount In USD))

How t

Answer 1

select date_1, SUM(amount*c.price) AS sum_by_day
from
(
    select *, max (date_2) as lastDate
    from tran_test AS t
    INNER JOIN cur_test AS c
    ON t.currency = c.currency AND date_1 >= date_2
    GROUP BY date_1;
) as t
INNER JOIN cur_test AS c
ON t.currency = c.currency AND lastdate = date_2
GROUP BY date_1;