How many flights depart to Hartsfield-Jackson Atlanta International from Chicago O'Hare International?
depart to refers to DEST; Hartsfield-Jackson Atlanta International refers to Description = 'Atlanta, GA: Hartsfield-Jackson Atlanta International'; depart from refers to ORIGIN; Chicago O'Hare International refes to Description = 'Chicago, IL: Chicago O'Hare International';
SELECT COUNT(FL_DATE) FROM Airlines WHERE ORIGIN = ( SELECT T2.ORIGIN FROM Airports AS T1 INNER JOIN Airlines AS T2 ON T1.Code = T2.ORIGIN WHERE T1.Description = 'Chicago, IL: Chicago O''Hare International' ) AND DEST = ( SELECT T4.DEST FROM Airports AS T3 INNER JOIN Airlines AS T4 ON T3.Code = T4.DEST WHERE T3.Description = 'Atlanta, GA: Hartsfield-Jackson Atlanta International' )
database name:db_id airline
Air Carriers table Air Carriers Cols: Code dtype integer, Description dtype text, 
Airports table Airports Cols: Code dtype text, Description dtype text, 
Airlines table Airlines Cols: flight date dtype text, operator carrier airline id dtype integer, tail number dtype text, operator carrier flight number dtype integer, origin airport id dtype integer, origin airport sequence id dtype integer, origin city market id dtype integer, ORIGIN dtype text, destination airport id dtype integer, destination airport sequence id dtype integer, destination city market id dtype integer, destination dtype text, scheduled local departure time dtype integer, departure time dtype integer, Departure delay dtype integer, departure delay new dtype integer, arrival time dtype integer, arrival delay dtype integer, arrival delay new dtype integer, CANCELLED dtype integer, cancellation code dtype text, scheduled elapsed time dtype integer, actual elapsed time dtype integer, carrier delay dtype integer, weather delay dtype integer, National Aviavtion System delay dtype integer, security delay dtype integer, late aircraft delay dtype integer, 
