How to have a subquery from few queries in Influx?

If you have (f.e.) two queries, you may want to join them and to make a query on top of joined result of both previous queries. How to join them?

Query1:

select mean(value) as mean_rd from foo  where type_instance='rd'

Query2:

select mean(value) as mean_wr from foo  where type_instance='wr'

Query 3:

Select mean_wr + mean_rw from (previous two)

Answer

Select max(mean_wr) + max(mean_rw) from  \
(select mean(value) as mean_rd from foo  where type_instance='rd'),
select mean(value) as mean_wr from foo  where type_instance='wr'

Put each request in brackets and join them by coma. Use ‘max’ for each value, as influx have trouble to operate on joined results without some kind of aggregate.