id       type      sum_cost         date_time
--------------------------------------------------
a1        pound     500        2019-04-21T10:50:06
b1        euro      100        2019-04-21T10:40:00
c1        pound     650        2019-04-21T11:00:00
d1        usd       410        2019-04-21T00:30:00

_id , start_time, end_time, pound_cost, euro_cost, count

_id   start_time           end_time              pound_cost  euro_cost  count
-----------------------------------------------------------------------------
 a1  2019-04-21T09:50:06  2019-04-21T10:20:06      500           0        1
 b1  2019-04-21T09:40:06  2019-04-21T10:10:00       0           100       1
 c1  2019-04-21T10:00:00  2019-04-21T10:30:00      650           0        1
 d1  2019-04-20T23:30:00  2019-04-21T00:00:00       0           410       1