Show all the locations where some cinemas were opened in both year 2010 and year 2011.
SELECT LOCATION FROM cinema WHERE openning_year  =  2010 INTERSECT SELECT LOCATION FROM cinema WHERE openning_year  =  2011
locations where cinemas opened in both year 2010 and 2011 refers to INTERSECT operation between cinemas with opening_year = 2010 and opening_year = 2011;