Question

SQL --

PROBLEM 4. At least two options for a single-airline round-trip.
-- Find cities where there are at least two companies, where
-- each company operates round-trip routes between two cities

Airline AirlinelD Source SourcelD Destination DestinationlD Codeshare Stops Equipment BNI BNI CNC CNC CNC None None None None None 7162 7161 3830 3678 3830 KLN KYK ORD STL ORD 3531 7162 5726 5726 4042 146 ADQ 20 20 3E 10739 BRL 3E 10739 BRL 3E 10739 DEC 146 4

Answer 1

In this table company is not mention

in my opinion there is one more table in which city and company are attributes

if company mention in question is airline then sql query is

table2= city company

table1 = company source destionation

select source from table1 as c1, tabel1 as c2 where c1.source=c2.destination and c1.destination=c2.source and company=(select company from table2 group by company having count>2)

in case of any query please give the complete table......