Give me a list of cities whose temperature in Mar is lower than that in July and which have also served as host cities ?
SELECT T1.city FROM city AS T1 JOIN temperature AS T2 ON T1.city_id   =   T2.city_id WHERE T2.Mar  <  T2.Jul INTERSECT SELECT T3.city FROM city AS T3 JOIN hosting_city AS T4 ON T3.city_id   =   T4.host_city
cities whose temperature in Mar is lower than that in July refers to T2.Mar < T2.Jul; cities that have served as host cities is determined by joining city with hosting_city; list of cities refers to SELECT T1.city;