Influxdb subquery to count top X -

i'm exited have subqueries in influxql started exploring encountered problem. want use subquery top x of measurement visits country

when query measurement:

select count("visit_count") daily_visit "visits channel" time > now() - 24h group country 

i result this:

name: visits channel tags: country=vietnam time                daily_visit ----                ----------- 1491501463914120735 14  name: visits channel tags: country=zambia time                daily_visit ----                ----------- 1491501463914120735 15 

that looks good, country tag , thought should able use in subquery top visits country:

select country,top(daily_visit,10) visits (select count("visit_count") daily_visit "visits channel" time > now() - 24h group country) 

but gives me empty country column:

time                country visits ----                ------- ------ 1491501689195632928         58 1491501689195632928         31 1491501689195632928         27 1491501689195632928         25 1491501689195632928         23 1491501689195632928         22 1491501689195632928         22 1491501689195632928         21 1491501689195632928         21 1491501689195632928         21 

seems i'm missing something? tag (country) problem?