What campuses are located in Northridge, Los Angeles or in San Francisco, San Francisco?
SELECT campus FROM campuses WHERE LOCATION  =  "Northridge" AND county  =  "Los Angeles" UNION SELECT campus FROM campuses WHERE LOCATION  =  "San Francisco" AND county  =  "San Francisco"
located in Northridge, Los Angeles refers to LOCATION = 'Northridge' AND county = 'Los Angeles'; located in San Francisco, San Francisco refers to LOCATION = 'San Francisco' AND county = 'San Francisco'; combining results from two locations uses UNION;