Combine two telegraf host measurements

I’m trying to find a way to add all hosts into a single value, so for example if host1 reports 200MB RAM and host2 120MB RAM, I’d like it to return 320MB at that point in time.

This gives me them overlayed, as generated by chronograf:

SELECT mean("used") AS "mean_used" FROM "telegraf"."autogen"."mem" WHERE time > :dashboardTime: AND time < :upperDashboardTime: GROUP BY time(:interval:), "host" FILL(null)

Looking at the InfluxQL docs, I am not quite sure how I could add all hosts dynamically at every point in time now though.