Hello,

I’m looking to calculate the sum of two fields and then perform a calculation on them to workout the difference.

In the code below I am calculating the sum of “cost” and the sum of “new_value” which works fine. However, I now want to calculate “new_value - cost”

I thought about using pivot() but the produced tables below (original and new_value) don’t have any _time columns.

```
original = from(bucket: "inventory")
|> range(start: 1970-08-28T22:00:00Z)
|> filter(fn: (r) => r["_field"] == "cost")
|> last()
|> group(columns: ["_field"])
|> sum(column: "_value")
|> map(fn: (r) => ({ r with _value: r._value - 1500.01 }))
new_value = from(bucket: "inventory")
|> range(start: v.timeRangeStart)
|> filter(fn: (r) => r["_field"] == "new_value")
|> last()
|> group(columns: ["_field"])
|> sum(column: "_value")
```