FluxLang - Math operation with two variables without time

Fluxlang
,
1

Hi !

With many syntax tested, i have a issue to understand how to make this: i have some wallet, with balance inside. I want to sum all coin, and then, multiply it with exchange rate… But, when i make sum, i dont have any “time” field or other to make a join…
For example:

currency = from(bucket: "default_bucket")
    |> range(start: v.timeRangeStart, stop: v.timeRangeStop)
    |> filter(fn: (r) => r._measurement == "currencies")
    |> filter(fn: (r) => r["_field"] == "eur")
    |> filter(fn: (r) => r["from"] == "ETH")
    |> truncateTimeColumn(unit:1m)
    |> last()

balance = from(bucket: "default_bucket")
  |> range(start: v.timeRangeStart, stop: v.timeRangeStop)
  |> filter(fn: (r) => r["_measurement"] == "balance")
  |> filter(fn: (r) => r["_field"] == "balance")
  |> filter(fn: (r) => r["coin"] == "eth")
  |> last()
  |> group()
  |> sum()

How can i make this simple math opération with two mesurements ?

Thanks in advance,