The where clause specifies which rows are to be updated. For example, in the unlikely event that Northern California is renamed Pacifica (abbreviated PC) and the people of Oakland vote to change the name of their city to College town, this is the way to update the authors table for all former Oakland residents whose addresses are now out of date:
update authors set state = "PC", city = "College Town" where state = "CA" and city = "Oakland"
You must write another statement to change the name of the state for residents of other cities in Northern California.
