Final answer:
An update query is used in a searchable database where multiple records need to be changed at once, such as updating book prices in a bookstore database.
Step-by-step explanation:
One example of a situation where you would use an update query is if you have a database for a bookstore and need to alter the price of all books in a particular genre due to a promotional discount. To efficiently change the prices in one operation without manually editing each record, an update query can be constructed that specifies the criteria for the books to be updated (e.g., all books within the 'Mystery' genre) and the new price to be set.