Database: bike_1
Question: How many trips started from Mountain View city and ended at Palo Alto city?
SQL: select count(*) from station as t1 join trip as t2 join station as t3 join trip as t4 on t1.id  =  t2.start_station_id and t2.id  =  t4.id and t3.id  =  t4.end_station_id where t1.city  =  "mountain view" and t3.city  =  "palo alto"