if you use incrementall load, save the load from where you fetch data With max(LoadingDate) as a New qvd.
then concatenate the New qvd with the previous qvd, the New qvd need to be first in script then the previous.
In the script where you load previous add where Exists (YourKey).
It will then find the value from New qvd where you have changed price or rates.
when it concatenate it With the old qvd the row With the same key is already there and will not add the second row.