Feature request: Not Exists

[Njanderson]

I would expect the following queries to be comparable, but alas I think NOT EXISTS does not parse.

schema sch_flights(fid:int,
    year:int,
	month_id:int,
	day_of_month:int,
	day_of_week_id:int,
	carrier_id:int,
	flight_num:int,
	origin_city:int,
	origin_state:int,
	dest_city:int,
	dest_state:int,
	departure_delay:int,
	taxi_out:int,
	arrival_delay:int,
	canceled:int,
	actual_time:int,
	distance:int
);

schema sch_carriers
(
	cid:int,
	name:int
);

SCHEMA sch_months
(
	mid:int,
	month:int
);

SCHEMA sch_days
(
	did:int,
	day_of_week:int
);

table Flights(sch_flights);
table Carriers(sch_carriers);
table Weekdays(sch_days);
table Months(sch_months);

query q1 `select distinct F1.origin_city as orig from Flights F1
where not exists(	select * from Flights F2
					where F2.actual_time >= 180
					and F2.origin_city = F1.origin_city )`;

query q2                -- define query q2 likewise
`select distinct F1.origin_city as orig
from Flights F1
where not exists(	select * from Flights F2
					where F2.actual_time >= 180
					and F2.origin_city = F1.origin_city )`;

verify q1 q2;           -- does q1 equal to q2?