Trying to get Count Distinct across multiple columns

Hey Folks,

Trying to figure out an equivalent for the following with influx.

SELECT COUNT(DISTINCT Useragent), COUNT(DISTINCT CountryId), COUNT(DISTINCT resolverID) from table where (time >= ‘2018-01-01 00:00:00’ AND time < ‘2018-01-02 00:00:00’)

Useragent, CountryID and ResolverID are all tags. I found SHOW TAG KEY CARDINALITY but how can I use this for multiple Tags?

If I have to revert these tags to fields how do we keep index performance with multi-tb datasets

This is probably something that is easy so please forgive if this is a daft question!