This example adds the number 1 to the phone extension of employees who work at the office in San Francisco:
a) UPDATE employees SET phone_extension = phone_extension + 1 WHERE office = 'San Francisco';
b) UPDATE employees SET phone_extension = phone_extension + 1 WHERE city = 'San Francisco';
c) UPDATE employees SET phone_extension = phone_extension + 1 WHERE office_location = 'San Francisco';
d) UPDATE employees SET phone_extension = phone_extension + 1 WHERE location = 'San Francisco';
