How do I add values of multiple queries?

For example I have values of data transferred for all my network interfaces how do i add them based on the interfaces that I want. I have queries created for each of the interfaces via the gui. IE query A contains all the traffic for eth0, B for eth1… How can I create a query for example to add values in query A, C, E togother?

Is each of your interfaces stored in a separate measurement or are they all in the same measurement with a different tag for each interface?

You should probably look into merging or joining:

If everything is in a single time series you can just omit any group by you might be using.