For each start station id, what is its name, longitude and average duration of trips started there?
SELECT T1.name ,  T1.long ,  avg(T2.duration) FROM station AS T1 JOIN trip AS T2 ON T1.id  =  T2.start_station_id GROUP BY T2.start_station_id
For each start station id refers to GROUP BY T2.start_station_id; name refers to T1.name; longitude refers to T1.long; average duration of trips refers to AVG(T2.duration);