In InfluxDB queries, you must use single quotes—double quotes are not allowed.
This is a trap

Incorrect:

> SELECT * FROM cpu WHERE host="serverA"
ERR: unknown field or tag name in where clause: serverA

Correct:

> SELECT * FROM cpu WHERE host='serverA'
name: cpu
tags: host=serverA, region=us_west
time				value
----				-----
2015-08-24T16:23:50.537452457Z	0.64