Examples
Media store: the Chinook database in this video represents a digital media store. With a few mouse clicks, from an artist you can go to his albums, the tracks of the albums, the customers who bought the tracks.
Bank: with a few mouse clicks, from a single operation, get the source and destination account, the account owners, which other operations was made in the same day between the accounts.
Hospital: with a few mouse clicks, from a patient, find the reason of the hospitalization, the insurance data, the clinical history, which other patients are in the hospital for the same reason.
You can do the same with standard SQL queries or with views, but in this way it is much faster.