select
COUNT(*) count_departured,
SUM(case when actual_departure-scheduled_departure>'00:30:00' then 1 else 0 end) count_delayed,
round(SUM(case when actual_departure-scheduled_departure>'00:30:00' then 1 else 0 end)*100.00/COUNT(*), 2) delayed_flights_rate
from flights
where departure_airport='DME' and to_char(scheduled_departure, 'YYYY-MM')='2017-08' and status='Arrived'
;
select * from query_cost('select
COUNT(*) count_departured,
SUM(case when actual_departure-scheduled_departure>''00:30:00'' then 1 else 0 end) count_delayed,
round(SUM(case when actual_departure-scheduled_departure>''00:30:00'' then 1 else 0 end)*100.00/COUNT(*), 2) delayed_flights_rate
from flights
where departure_airport=''DME'' and to_char(scheduled_departure, ''YYYY-MM'')=''2017-08'' and status=''Arrived''');